Barack Obama has been re-elected as President of the United States.
Voting was close in the race for the White House with Republican challenger Mitt Romney needing to win key swinging states.
However all major television networks in the US have predicted an Obama victory.
With 270 needed for victory the current numbers are 274 to Mitt Romney's 201.(All times AEDT)
5:53pm: The president says he will return to the White House with greater determination than ever.
Whether I earned your vote or not, I have listened to you.
I have learned from you and have learned from you and you have made me a better president.
With your stories and your struggles, I return to the White House more determined and more inspired than ever about the work there is to do and the future that lies ahead.
5:50pm: Obama revives his campaign slogan, urging Americans to move forward.
That's where we need to go. We will disagree, sometimes fiercely, about how to get there.
As it has for more than two centuries, progress will come in fits and starts. It is not always a straight line or a smooth path.
By itself, the recognition we have common hopes and dreams won't end the gridlock or solve all our problems or substitute for the painstaking work of building consensus and making the difficult compromises needed to move this country forward.
That common bond is where we must begin.
5:47pm: The president says democracy in the US can be messy:
Democracy in a nation of 300 million can be noisy and messy and complicated.
We have our own opinions. Each of us has deeply held beliefs and when we go through tough times, when we make big decisions as a country, it necessarily stirs passions, stirs up controversy.
That won't change after tonight and it shouldn't.
These arguments we have are a mark of our liberty.
We can never forget that as we speak, people in distant nations are risking their lives right now just for a chance to argue about the issues that matter, the chance to cast their ballots like we did today.
5:44pm: Bad news for the first daughters, Sasha and Malia ... looks like they won't be getting another dog like they did after their dad's first election win.
Sasha and Malia, before our very eyes you're growing up to become two strong, smart, beautiful young women just like your mum.
I'm so proud of you guys, but I will say that for now one dog's probably enough.
5:43pm: Love for first lady Michelle Obama:
I wouldn't be the man I am today without the woman who agreed to marry me 20 years ago.
Let me say this publicly: Michelle, I have never loved you more.
I have never been prouder to watch the rest of America fall in love with you too as your nation's first lady.
5:42pm: Obama offers warm words for his vanquished challenger Mitt Romney.
We may have battled fiercely, but it is only because we love this country deeply and we care so strongly about its future.
From George to Lenore to their son Mitt, the Romney family has chosen to give back to America through public service and that is a legacy we honour and applaud tonight.
In the weeks ahead I also look forward to sitting down with governor Romney to talk about where we can work together to move this country forward.
5:41pm: The president thanks those who voted for the first time, or "waited for a very long time".
5:39pm: Obama says the voters have helped America move forward because "you reaffirmed the spirit that has triumphed over war and oppression".
The spirit that has lifted this country from the depths of despair to the great heights of hope.
The belief that while each of us will pursue our own individual dreams, we are an American family and we rise or fall together as one nation and as one people.
5:37pm: To the raptures of the crowd and overtures of Stevie Wonder's Signed, Sealed, Delivered, Barack Obama arrives on stage to address his supporters.
5:34pm: US house speaker John Boehner says the result is a "mandate forÂ both partiesÂ to find common ground".
The American people re-elected the president, and re-elected our majority in the House.Â
If there is a mandate, it is aÂ mandate forÂ both partiesÂ to find common ground and take steps together to help our economy grow and create jobs, which is critical to solving our debt.Â
I offer sincere congratulations to president and Mrs Obama and to vice president and Dr Biden.Â
IÂ wish Mitt, Ann, Paul, Janna and their families well, and thank them for having carried the banner of our party and our principles with strength, grace, and courage.
5:31pm: Obama is in the building!
5:25pm: British PM has taken to Twitter:
Warm congratulations to my friend . Look forward to continuing to work together.
5:24pm: ABC correspondent Kim Landers and election analyst Antony Green discuss the US political landscape that lies ahead after Barack Obama's re-election.
5:21pm: As Barack Obama edges further ahead in the popular vote nationwide, it becomes clearer that Mitt Romney was only able to regain North Carolina and Indiana for the Republicans.
5:18pm: Prime Minister Julia Gillard has issued a statement congratulating Barack Obama on his re-election. It read in part:
On behalf of the Government and people of Australia, I offer warm congratulations to president Barack Obama on his re-election and wish him every success for his second term in office.
Australia has worked closely with president Obama and his administration over the past four years.Â
I look forward to continuing this friendship.Â
US leadership remains vital to meeting global challenges; international financial stability and global economic growth, peace and security, and the impacts of our changing climate.Â
Australia has a long history of working with the United States to make a difference on these global challenges.
I look forward to continuing to do so with president Obama on behalf of the people we serve.
5:16pm: Barack Obama leaves his hotel and is on his way to address his supporters in Chicago.
5:04pm: The crowd in the Chicago convention centre is now at near fever pitch anticipating the arrival of Barack Obama.
5:00pm: Romney says the US is at a critical point and that he ran for office because "I'm concerned about America".
That nation is at a critical point ... Our leaders have to reach across the aisle to do the people's work.
We look to Democrats and Republicans ... to put the people before the politics.
I believe in America, I believe in the people of America.
4:57pm: The Republican challenger singles out his running mate Paul Ryan for special praise, as well as thanking his wife and family.
Besides my wife Ann, Paul (Ryan) is the best choice I've ever made.
She would have been a wonderful first lady. She has been that to me ...
I thank my sons for their tireless work, and thank their wives and children as their husbands and dads have spent so many weeks away from home.
Paul and I have left everything on the field. We have given our all to this campaign.
Ann and I join with you to earnestly pray for him (Obama) and the nation.
4:55pm: Mitt Romney takes to the stage to address his supporters.
I have just called President Obama to congratulate him on his victory.
This is a time of great challenge for America and I pray that the president will be successful in guiding our nation.
4:50pm: Mitt Romney calls Barack Obama to concede defeat. The Republican challenger is expected to address his supporters in a few minutes.
4:48pm: Chanting "Four more years!" and "USA, USA!," a crowd of well-wishers is dancing and celebrating outside the White House. Obama supporters braved the chilly weather to wave American flags, dance and high-five strangers outside the president's official residence. Union activist Nicole Arow, 28, said she was "thrilled and relieved" to learn about Obama's victory over Mitt Romney, adding: "Joy. That's what I feel."
"I'm incredibly excited," gushed Justin Pinn, a 22 year-old government student at Georgetown University. "I feel that my hope is renewed and I'm ready to fight the good fight. It's a great day to be an American."
4:44pm: CNN's Candy Crowley on the waiting game for Romney.
"Still very quiet at Romney HQ. Paul Ryan is in the general area. We're expecting him to come first. But so far we've not got any definitive word."
4:39pm: Antony Green calls Virginia and its 13 electoral college votes for Obama, taking his total to 303. Meanwhile, The New York Times reports Florida is still a very tight race, with Obama ahead of Romney by about 0.5 per cent.
4:35pm: Obama now takes lead in popular vote by about 28,000 votes.
4:32pm: Former foreign minister Alexander Downer tells ABC News 24 that the Tea Party had a lot to answer for.
"I think for me the really interesting thing is that within the Republican Party, they're going to have to resolve the tension between the mainstream traditional Republicans, sometimes referred to as the Republican establishment, and the Tea Party people.
"My guess is - I might be wrong about this and this might be a bit more wishful thinking on my part - but my guess is that Republicans generally will realise that the Tea Party campaign has really wrecked their chances of turning Barack Obama into a one-term president, not Mitt Romney."
4:28pm: There is nothing in the popular vote as Obama continues to close the gap. With around 73 per cent counted nationally, Romney leads Obama 49,028,980 to 49,028,645 - a lead of just 335 votes.
4:23pm: Another tweet from president
We're all in this together. That's how we campaigned, and that's who we are. Thank you. -bo
4:20pm: US stock futures and the greenback fell as television networks projected Barack Obama's re-election, signalling no dramatic shift in US economic policy.
4:10pm: ABC election analyst Antony Green calls Nevada for Obama. This takes the ABC's projection of the president's electoral college vote to 290.
4:08pm: There were a lot of other issues decided on election day in the US. Among them was the state of Maine becoming the first to have gay marriage delivered through popular vote. Colorado approves the recreational use of marijuana.
4:06pm: New York Times calls the battleground state of Virginia for Obama.
If it wasn't over before... it surely is now.
4:03pm: Some Republicans are refusing to give up.
George W Bush adviser Karl Rove is on Fox News and appears to be urging them to rescind their decision to call Ohio for Obama, and therefore their presidency.
3:40pm: CNN reports Mitt Romney is not yet ready to concede.
3:26pm: Obama picked up the swing states of New Hampshire, Michigan, New Mexico, Iowa, Wisconsin, Pennsylvania, Minnesota, and Ohio. Florida and Virginia are still too close to call, but even if he won them, they would not give Romney enough Electoral College votes to put him over the top. Romney looks poised to do better in the overall popular vote.
3:17pm: NBC calls the election for Barack Obama
3:14pm: Antony Green gives Iowa and New Mexico to Obama. It's 250-206 and Obama only needs another 20 college votes to win it. Former Florida governor Jeb Bush has called Mitt Romney to say Florida is lost.
3:10pm: Advantage Obama: Lots of cheering at Obama HQ as CNN gives Iowa - part of the mid-western firewall - to their man. CNN showing cheering crowds in downtown Chicago.
3:06pm: Antony Green has just called North Carolina, Missouri, Montana to the Republicans: Washington to the Democrats. Obama has 239 Electoral College votes, Romney has 206. 270 votes needed for victory.
Lisa Millar says people are starting to leave Romney's rally in Boston. "It's even more subdued inside than what we've been reporting," she says. Alex Castellanos, Republican political commentator, has told CNN "I'm going for the hemlock".
3:04pm: Snapshot: Ohio, Florida and Virginia hold the keys to the White House Obama holds small leads in Ohio and Florida. Romney leads narrowly in Virginia. Romney must win all three of those states to win the White House. Obama is set for victory if he wins one of those states. California has just closed and the networks have given to Obama. Analysts say Romney's chances are fading fast.
2:58pm: Craig McMurtrie in Chicago says Obama has left his house and will soon be on his way to his election night rally. The mood there is jubilant, with cheering and yelling as the networks call states in their favour.
In contrast, the mood at Romney HQ in Boston is plummeting.
"The pathway to the presidency is shrinking. You can feel it in the room." CNN's Candy Crowley at Romney HQ says.
2:55pm: Obama is still ahead in Florida with 92 per cent of precincts counted.
2:41pm: The numbers are Obama 227, Romney 178 with 270 needed to win.
2:46pm: US ambassador to Australia Jeffrey Bleich says he's observed Australia's system of compulsory voting with interest.
Mr Bleich says when he does return to the US, he will be more aware of the flaws in the US system of voluntary voting on a weekday.
"I think Americans would benefit from thinking more seriously about the need for everyone to vote, however that's accomplished, and that's one idea that I think I would bring back," he told ABC News 24.
2:45pm: Al Gore has tweeted that "I am confident in saying that President Obama is going to carry the state of Florida tonight."
2:41pm: Antony Green is now giving Arizona to the Republicans. The college numbers are Obama 227, Romney 178. 270 needed to win in what Antony calls this "festival of democracy".
2:36pm: How can Romney win from here? ABC election expert Antony Green says that "Beyond 191 [Electoral College votes] they need to win Florida, North Carolina, Virginia and Ohio and another state. We've just given Wisconsin away, so the numbers are getting much, much tighter. We started this coverage several hours ago and we're waiting on Virginia, North Carolina and Florida."
2:32pm: Although he leads in the Electoral College, Obama trails on the raw numbers of votes counted nationally. He has 48.1 per cent against Romney's 50.6 per cent.
2:22pm: The US networks have called the following states:
Romney: Louisiana, Montana, Alabama, Arkansas, Georgia, Indiana, Kansas, Kentucky, Mississippi, Oklahoma, South Carolina, Tennessee, West Virginia, North Dakota, South Dakota, Nebraska, Texas, Utah, Wyoming.
Obama: Pennsylvania, New Hampshire, Michigan, New York, Wisconsin, Connecticut, District of Columbia, Delaware, Illinois, Massachusetts, Maryland, Maine, New Jersey, Rhode Island, Vermont.
2:11pm: President Barack Obama has won the battleground state of Wisconsin, depriving Mitt Romney of a key target that could help him win the White House.
2:00pm: US network CNN is reporting that it is virtually impossible for the Republicans to regain control of the Senate.
In one the highest-profile Senate races, in Indiana, Richard Mourdock, who made controversial remarks on rape and abortion, appears to have lost the race to Democrat Joe Donnelly.
1:58pm: Antony Green has given New Hampshire to Obama, taking him to 217 Electoral College votes.
1:55pm: One of Australia's most pre-eminent America-watchers from the ANU, John Hart, says something is going on in Virginia:
"One of the interesting things to me is the fact that the big networks are not calling any of these key battleground states.
"In Virginia, the polls closed four hours ago.
"There's something like 65 per cent of the vote counted. They're not calling it. What's going on? It is a close race but I guess even closer than a lot of people expected."
1:42pm: Lisa Millar is in Boston at Romney HQ: She says a sense of pessimism is creeping in as the electoral pathway to the White House narrows. The big screens showing Fox News have been turned down.
"All the attention through this entire campaign was about Ohio and it still is about Ohio," she told ABC News 24.
"Certainly there's tension, pessimism, they're not liking what they're seeing."
1:38pm: Here's the situation: Florida, Ohio and Virginia too close to call. Obama projected to win Pennsylvania, Michigan, Wisconsin. Neck and neck in Florida, which Obama can afford to lose but Romney must win. Romney must win Ohio to keep his chances alive.
1:34pm: Antony Green has called Pennsylvania for Obama. That gives Obama 213 Electoral College votes, Romney has 167. 270 votes needed to win
1:33pm: Fox and NBC are giving Wisconsin to Obama. That's Paul Ryan's home state.
1:32pm: US networks are predicting the Republicans will have control of the House of Representatives. Not unexpected, but it would make life difficult for Obama if he gets back in.
1:28pm: John Barron says that projections Obama will hold Pennsylvania is very bad news for Romney.
"That is significant because if Mitt Romney was blocked in Ohio, and all the polls were suggesting that Barack Obama was in front there, his only avenue to 270 votes was through Pennsylvania.
"He threw $50 million into TV advertising in the last week, it hasn't worked.
"So, as of right now, it all comes down to Ohio. And as we've been seeing, Florida is very close. In Virginia it could be that Mitt Romney is regaining a bit of ground there, but Virginia matters for nothing if he can't get back in front in Ohio.
1:24pm: Dr David Smith from the US Study Centre is on ABC News 24 and says he'd "definitely prefer to be in president Barack Obama's shoes right now.
"The most promising thing for him is that the actual votes that are coming in seem to mirror what the public opinion polls were saying before the election - which was that he would win.
"Already we can see that the Republican dreams of getting Michigan or Pennsylvania are off the table.
"It is absolutely neck and neck in Florida, which is a state that Romney absolutely has to win but Obama doesn't have to win.
"Really the brightest spot for Romney at the moment is Virginia, where he has a lead of over 100,000 votes with about half the votes counted, but we are still waiting for votes to come in from the suburbs of DC.
"So you'd really prefer to be Obama right now."
But he says: "Florida has a rule where if it's within 0.5 per cent there's an automatic recount triggered. So that could be what we're looking at today."
1:18pm: Fox, CBS and NBC are all projecting Obama to win Pennsylvania, despite Romney's late push there.
1:16pm: Celinda Lake, Democratic pollster and strategist, has told ABC News 24 the party is confident and she hopes the result will be known in a couple of hours:
"Frankly we're feeling better than we thought we were going to feel.
"In Florida the vote was the same as in 2008, which we did not expect and we're seeing the surge in vote among the non-Cuban Latino voters, which we did expect.
"In northern Virginia and Virginia we're doing better than expected and in Ohio while there are still many, many votes to be counted, turnout was high and the networks have called it lean [towards] Obama.
"So if we win Florida and Virginia and Ohio the night is over."
1:12pm: Antony Green gives Michigan to Obama. That makes it 193 electoral college votes to Obama, 167 to Romney. 270 votes needed to win.
1:09pm: Professor Stephen Farnsworth explains how some Americans will still be voting even once the polls in their states have officially closed.
1:07pm: Michigan going to Obama is significant because it's where Romney was born, and where his father was governor.
1:06pm: Exit polls have Colorado too close to call, with each candidate on 48 per cent. US networks are starting to call for Michigan - American ABC, CBS, CNN and Fox News all declaring for Obama.
1:03pm: CNN predicts Romney to win Texas, Kansas, Louisiana, Nebraska, North Dakota. The network gives Michigan, New York and New Jersey to Obama. More exit polls coming soon.
12:52pm: The scene at the Boston Convention Centre ahead of Mitt Romney's election night event.
12:50pm: Jane Cowan reports: Obama has been eating dinner at home with his family and aides say he is "calm, serene and excited".
He's told reporters he's written two speeches, but doesn't expect to have to deliver the losing one.
12:44pm: Craig McMurtrie says hundreds of supporters are being bussed into Obama's Chicago HQ. The mood there is still tense but people think the president "now has the narrowest of edges".
12:40pm: Colorado and Wisconsin will close at 1:00pm AEDT.
12:38pm: The long delays at polling booths mean many voters are still waiting to cast their ballots even in states where the polls have officially closed. Virginians could still be voting for another two-and-a-half hours.
12:32pm: Obama is leading 58 per cent to 40 per cent in Ohio with 20 per cent of the vote in - but the booths which have reported are in Democratic areas and Antony Green says it's still too early to draw firm conclusions.
Arkansas has just closed and it's in the bag for the Republicans.
12:26pm: Ohio, Virginia and Florida are all still too close to call.
12:18am: The US networks have called the following states:
Romney: Alabama, Georgia, Indiana, Kentucky, Mississippi, Alabama, Oklahoma, South Carolina, Tennessee, West Virginia
Obama: Connecticut, District of Columbia, Delaware, Illinois, Massachusetts, Maryland, Maine, New Jersey, Rhode Island, Vermont.
12:16pm: Reporters are gathering in Chicago ahead of Obama's rally later today. The mood in Obama HQ is reported to be tense.
12:15pm: Mitt Romney told reporters on his jet that his team will be successful because they've "put it all on the field, left nothing in the locker room"
12:12pm: Antony Green: "Essentially all the exit polls are looking like the opinion polls you've seen for the last few weeks - that states like Pennsylvania, Ohio, Florida are close, and at this stage no-one is giving away any of those states." He says it's going to be a long night - or afternoon, in our neck of the woods.
12:06pm: This video just in of Mitt Romney speaking on his campaign jet earlier.
12:00pm: A huge swag of states have just closed, and 175 Electoral College votes are about to come online. CNN is projecting Obama will win Connecticut, Delaware, District of Columbia, Maryland, Massachusetts, Maine, and Rhode Island. It says Romney will win Oklahoma.
11:56am: John Barron says exit polls show 79 per cent of voters in Ohio today are white, down 5 per cent on four years ago.
"That's generally good news for down Barack Obama," he says.
"They've also said by a margin of 56 per cent to 44 per cent that [Obama's] auto bailout was a good thing."
11:52am: People in Queens, still without power after Sandy, listen to the election news on the radio.
11:50am: The rest of Florida; Pennsylvania; and New Hampshire will all close at the top of the hour.
11:49am: Lisa Millar reports from Romney's HQ in Boston and she says confidence is high in the Republican camp as the results start to trickle in.
"[Romney's] written a victory speech, 1000 words and clearly he's not planning to do anything other than be having a party here this evening in the Convention Centre behind me," she said.
"Bus loads of people are you turning up. They're looking and feeling pretty confident, walking in cheering. There were school children, high school children, who have turned up who have been volunteering and helping getting people to the polls here in Massachusetts.
"Certainly, nothing but confidence in Boston from the Romney camp, but as those figures keep coming in, we'll see whether that confidence dies away as the Obama camp suggests it will."
11:45am: So far the US networks have called Indiana, Kentucky, South Carolina and West Virginia for Romney; and Vermont for Obama. All as expected.
11:40am: Antony Green says more than 1 million votes have already been counted. None of the US networks are prepared to call Ohio or Florida yet. He says Indiana will go to the Republicans.
11:35am: Florida is on two time zones. The last polls there close at midday AEDT. But with 23 per cent of the vote counted, CNN says the state is running 52 per cent to 48 per cent in Obama's favour.
11:32am: CNN exit poll has Obama leading 51 per cent to 48 per cent in must-win Ohio.
11:31am: CNN is giving West Virginia to Romney but says Ohio and North Carolina are too close to call.
11:30am: Voting has closed in Ohio, West Virginia and North Carolina.
Antony Green says Florida is running 50.2 per cent to Romney, 49.2 per cent to Obama, but it's very early in the count.
11:25am: Professor Stephen Farnsworth, of the University of Mary Washington, talks about the states upon which the US presidency hinges as the first polls close.
11:21am: With 5 per cent of the vote counted in Florida, the result is 50-50, according to CNN.
11:17am: The next big results are due around 11:30am when the key swing states of Ohio, West Virginia and North Carolina close.
Keep an eye on Ohio, Wisconsin and Iowa, the states which have been dubbed Obama's "mid-west firewall". If the firewall holds for Obama, Romney's path to the White House is very, very difficult.
11:12am: Reuters/IPSOS exit poll says first-time voters broke two-to-one for Obama nationally.
11:10am: Romney is leading exit polls in Indiana and Kentucky; the US networks give Vermont to Obama.
11:05am: Electoral votes are being allocated according to ABC election analyst Antony Green's call of the states.
11:04am: On a knife-edge: CNN exit poll in Virginia shows 49 per cent to Obama, and 49 per cent to Romney.
11:03am: An early boost for Obama? John Barron says CNN's Peter Hamby reports that a source in the Romney camp has told him that internal Republican polling over the weekend has Obama 5 per cent up in must-win Ohio.
"If that's the fact ...that is very good news for Barack Obama," Barron says.
11:00am: The polls have closed in the key state of Virginia.
ABC election analyst Antony Green has already called it in a swag of states which he says can be predicted ahead of time.
He says his tally gives Obama 177 Electoral College votes against 167 for Romney.
10:45am: 15 minutes to go until Virginia closes. The ABC's Jane Cowan says many analysts are pointing to a long night ahead, but she has given some tips for predicting the outcome as the polls close:
"Things to look for are what happens in Virginia. That's a must-win state for Mitt Romney where the polls will be among the first to close," she said.
"If the president for instance wins Virginia, Mitt Romney would virtually have to sweep the board of the remaining contested states to pull off a win.
"Equally if Mitt Romney wins Ohio people should settle in for a long night because that could signal that this much-hyped ground organisation of the Obama campaign is faltering."
10:40am: Barack Obama is out in front in American 7-Eleven stores, where an unofficial poll is being conducted based on purchases of coffee.
Shoppers are invited to get a "steaming hot cup of democracy" by choosing from either a blue Obama cup or a red Romney cup when they buy a coffee.
This morning Mr Obama is comfortably in front sitting on 59 per cent, while Mr Romney is on 41 per cent.
10:28am: Barrie Cassidy: "If Australia was the 51st state of America, we would get 30 Electoral College votes out of more than 500."
10:20am: After Virginia closes at 11am, the next states to close will be Ohio and North Carolina at 11:30am.
10:16am: The polls have closed in most of Indiana and the eastern part of Kentucky.
Polls closed at 10:00am AEDT in parts of the two states observing Eastern Standard Time. The states both straddle two time zones.
The results are unlikely to be decisive in the election as both are widely expected to vote for Mitt Romney.
10:08am: Republican strategist Liz Mair tells ABC News 24 that is key.
"Virginia is key. It's a very, very close race there. Everybody seems to recognise that it's exactly 50/50. If you see Virginia go early either way, I think that suggests that something could be going on that may put one candidate or another in a significantly better position than they expect it to be."
We'll have the results from the state live as they come in from from 11:00am.
Meanwhile, Mitt Romney has told a reporter that he's finished his victory speech. That's confidence. And Barack Obama's team won in his election day basketball game.
10:02am: Now less than an hour until the polls close in Virginia.
9:58am: Michael Rowland says the polls are putting Barack Obama ahead with 290 electoral college votes. But George W Bush's former strategist Karl Rove has predicted Mr Romney will get 285 electoral college votes.
"Republicans are telling us that these polls are all wrong, they're skewed towards the Democrats, the mechanisms used by pollsters are completely wrong," Rowland said.
"Their internal polling shows them that Mitt Romney has a much, much stronger chance than the public polls are showing."
Candidates need at least 270 votes to win.
Donald Betts, a former Democratic senator from Kansas, has told ABC News 24 that Americans feel there is a lot at stake in this year's election.
"Previous years the [voter] numbers have been lower because it hasn't been such a dramatic election," he said.
"In this case it's life or death. In some American's eyes this is the election. I mean it's the election for the future of our families and our children."
The Pew Research Centre has surveyed Hispanic voters in the US. They say there are a record 24 million Latinos eligible to vote and of those likely to vote, 66 per cent are set to back Obama, to 27 per cent Romney.
9:42am: There have been a few reports of voting irregularities, with complaints of some glitches with electronic voting. Reuters reports that "voting appeared to go smoothly in most places, [but] complaints about procedures and possible irregularities surfaced sporadically across the electoral map. But there were no immediate claims of anything widespread or systematic enough to cast doubt on the credibility of the election outcome."
9:33am: Locals in the small Kenyan village where Barack Obama's late father grew up have held a mock US election.
But one Kenyan voter bad news for Mr Obama. He says Mitt Romney came to him in a dream last night so he now expects the Republican to win.
9:28am: Lisa Millar fills us in on some "inconsequential information that no one really needs to know" from Team Romney:
"In Ohio he had a burger and a frosty and we don't know if it was chocolate or vanilla," she said.
"But that's the kind of details that are currently being put out by the reporters who have faithfully for 18 monthsÂ covered every single move of Mitt Romney."
Meanwhile Barack Obama is reported to be playing basketball with former members of the Chicago Bulls in Chicago.
9:16am: New York Times election analyst Nate Silver puts Barack Obama's chances of winning today's election at higher than 90 per cent, saying the incumbent has in the final days of the campaign.
Silver, during the campaign, says a large number of polls across multiple states would have to be in error for Mitt Romney to win.
9:03am: It's now less than two hours until the polls close in Virginia. The ABC's Ben Knight says that with the polls so close, there are already concerns about how the vote counting will go.
"There's a real fear that this election will be decided long after tomorrow, in courtrooms in Florida and Ohio," he said.
On Friday, Ohio's Republican secretary of state ruled that voters themselves, not poll workers, were the ones who would fill out provisional ballot forms and if a mistake was made the ballot itself would be thrown out.Â
Democrat lawyers are now in court challenging this.
And in Florida there is another lawsuit over how long the polls were allowed to stay open for early voting. Hundreds of voters were turned away on the weekend when some polling stations closed early.
"The spectre of the 2000 vote - the infamous hanging chads in Florida - is in everyone's minds. It was decided in a Florida court. It won George W Bush the presidency, but many Democrats never accepted the legitimacy of the result," Knight said.
8:56am: From the photo desk: Members of the National Guard deployed on the Hurricane Sandy clean-up in New Jersey cast absentee votes:
8:50am: Mitt Romney took his campaign right down to the wire overnight, squeezing in visits to Ohio and Pennsylvania as voters headed to the polls. Here he thanks his supporters during a last-minute appearance in Ohio, saying "it is a big day for big change".
8:43am: ABC correspondent Craig McMurtrie is in Chicago, where Barack Obama is awaiting the voters' verdict on his four years in the White House.
He says the Obama camp is "projecting real confidence."
"These swing states that we've been speaking about for weeks, that run from Florida to Virginia to Ohio, even to New Hampshire, these are all states Barack Obama carried four years ago and carried pretty handsomely.
"He has to defend them all tonight. He probably won't hang on to them all, but from his perspective it's about defending those positions and making sure that they come up with this magic formula that gets them 270 electoral college votes.
"And the Obama camp is very confident that they have more pathways to that they have more pathways to that magic number than Mitt Romney."
8:38am: Democrat strategist Linda Moore-Forbes has told the ABC's Michael Rowland that Team Obama is confident.
"Feeling really good. The turnout seems really strong. What I'm definitely picking up is a strong turnout among young people," she said.
She says Mr Obama isn't campaigning today because it's a drain on resources.
And she says Mitt Romney's appearance in Pennsylvania today is more likely to energise Democrats than help the Republican campaign.
8:23am: In Dixville Notch, New Hampshire, the 10 eligible voters in town have the honour of being the first in America to have their ballots counted.
When the results came in overnight they had tied, with five residents backing Barack Obama and five behind Mitt Romney.
8:05am: Here's the state of play so far this morning: There are reports of long queues at polling booths across the US, and hopes voter turnout could be as high as 58 per cent. Obama has visited his campaign HQ in Chicago and thanked the volunteers who have worked for him. Romney squeezed in two last-minute campaign stops in Pennsylvania and Ohio. The first results have been tallied in Dixville Notch, where Obama and Romney tied on five votes. Results are also in from Hart's Location where Obama had 23 votes to nine for Romney.
7:53am: Leading US pollster John Zogby tells Michael Rowland that he expects Barack Obama to be re-elected as president with 290 Electoral College votes.
7:43am: Greeted with loud cheers of "Romney! Romney!" and "We love you Mitt!", Mitt Romney sounded confident as he thanked volunteers helping his campaign:
"Thank you so very much for being here today. It's critical because it is a big day for big change," he said.
"The country's been going in the wrong direction for the last few years and we're going to steer it back.
"I'm so excited about the prospects."
7:41am: Lisa Millar has spoken to voters in Boston who have had a long wait to cast their ballot.
Some say US elections should be held on the weekend so people have more time to get out and vote:
"The easier it gets the more people are going to participate. I mean this is a bit of a barrier for some people. A lot of people feel why go through this? It isn't worth it."
7:32am: There are still reports of long queues at polling booths across the US and there are hopes voter turnout could be as high as 58 per cent.
7:13am: Here's what voters in the key battleground state of Ohio had to say:
7:07am: The New York Post has endorsed Republican Mitt Romney.
The Rupert Murdoch-owned paper said Americans today have to make a fateful choice:
"Will they continue down the path to terminal indebtedness and endless economic decay - or will they try something different, something more hopeful?
Will they vote for Mitt Romney? We hope so."
7:00am: Mitt Romney has arrived in the swing state of Pennsylvania for more last-minute campaigning.
He is due to hold a rally in Pittsburgh shortly.
Meanwhile, analysts still say the vote is too close to call.
6:46am: Thomas Mann from the Brookings Institute speaks to Michael Rowland in Washington.
He says the race is close but Barack Obama is the favourite:
6:42am: The ABC's Lisa Millar is reporting from Boston, where Mitt Romney will hold his election night celebrations or commiserations.
While it's raining in Barack Obama's hometown of Chicago, Millar says Boston's weather is giving them a run for their money, with temperatures close to freezing.
She has also checked out preparations for tonight's post-vote party:
"How many security officers does it take to protect Mitt Romney's election night party? Too many to count. #Boston
6:35am: Mr Obama has thanked Mitt Romney for running a "spirited campaign".
"I want to congratulate governor Romney and his team for a hard fought race as well."
6:29am: Barack Obama visits his campaign HQ in Chicago and thanks the volunteers who have worked for him.
"It's a source of great optimism for me whenever I come to election day because I end up having so much confidence in the decency and goodness and wisdom of ordinary folks who are working so hard trying to move their own small piece of this country forward," he said.
6:20am: OVERNIGHT RECAP: The first results have been tallied in Dixville Notch, where Obama and Romney tied on five votes. Results are in from Hart's Location where Obama had 23 votes to nine for Romney. Both candidates have now cast their votes. Obama is spending the day in his hometown Chicago, where he has visited his campaign office. Romney is doing last-minute campaigning in swing states Pennsylvania and Ohio.
6:13am: Polls show Barack Obama has a slight advantage in several of the vital swing states - most notably Ohio.
5:55am: Apparently things got a little awkward at the Cleveland airport; Mitt Romney landed first, but when Joe Biden swooped in on Air Force Two the Republican was forced to wait on the tarmac until Mr Biden's motorcade had left.
Minutes later the tarmac became even more crowded when Republican vice presidential candidate Paul Ryan flew in.
5:48am: Republican challenger Mitt Romney and US vice president Joe Biden are both doing some last minute campaigning in Ohio.
In fact, the planes of both men are currently sitting on the same tarmac at Cleveland airport.
5:39am: NEWS JUST IN which may compound fears of a low voter turnout in areas battered by last week's hurricane, New York mayor Michael Bloomberg is now asking residents of some low-lying areas to evacuate by Wednesday (US time) ahead of another storm. NYC parks will also be closed.
5:27am: See what time polling booths close this morning in the battleground states:
5:26am: Last night North America correspondent Lisa Millar spoke to Lateline from Boston just before voting got underway. She said opinion polls had been level for weeks, but inched towards Mr Obama on the eve of the election:
Obama congratulates Romney on 'spirited campaign'
U.S. President Barack Obama congratulated Republican rival Mitt Romney on Tuesday for running a hard-fought race for the White House and expressed confidence he would win re-election during a stop at a local campaign office to thank volunteers.
"I ... want to say to Governor Romney congratulations on a spirited campaign. I know that his supporters are just as engaged and just as enthusiastic and working just as hard today," Obama said as volunteers made phone calls encouraging supporters to get to the polls.
"We feel confident we've got the votes to win, but it's going to depend ultimately on whether those votes turn out. And so I would encourage everybody on all sides just to make sure that you exercise this precious right that we have that people fought so hard for us to have."
Obama made calls to volunteers from the campaign office to thank them for working for his re-election.
"I expect that we'll have a good night, but no matter what happens, I just want to say how much I appreciate everybody who supported me, everybody who's worked so hard on my behalf," he said.
Opinion polls show Obama and Romney in a virtual dead heat, although the Democratic incumbent has a slight advantage in several vital swing states that could give him the 270 electoral votes needed to win the state-by-state contest.
Traditionally presidential candidates get media attention on Election Day by going to vote. But Obama cast his ballot in Chicago last month - part of his campaign's push to get its supporters to vote early.
So the president's visit to the office gave him a chance to get in front of the cameras, generate news coverage and encourage turnout.
Obama and Romney, a former Massachusetts governor and private equity executive, have fought a largely negative campaign. Obama's team attacked Romney for his business record, and Romney's team criticized the president for presiding over high unemployment and a slow economic recovery.
Obama's conciliatory comments represent the close of the bitter campaign and could appeal to last-minute undecided voters, who are turned off by the lack of bipartisanship in Washington.In addition to his campaign office stop, Obama is doing a round of interviews and is expected to play basketball with friends, a tradition for the sports-loving president on Election Day.