President Barack Obama, fighting for his top domestic priority, urged fellow Democrats in the House of Representatives to "vote yes" on Saturday on the broadest US health care overhaul in a half-century.
"This is our moment to deliver. I urge members of congress to rise to this moment, answer the call of history and vote yes for health insurance reform for America," he urged in a speech from the White House Rose Garden.
House Democratic leaders predicted their 258-seat majority would hold together enough to rally the 218 votes needed to pass the 10-year, trillion dollar bill over united opposition from the chamber's 177 Republicans.
"We will be making history with our vote," House Speaker Nancy Pelosi vowed after Obama made a rare in-person plea for Democratic unity in closed-door talks at the Congress.
The bill aims to extend health coverage to 36 million Americans who lack it now, create a government-backed insurance plan to compete with private firms, and end denial of coverage based on preexisting medical problems.
Democrats, who can afford 40 defections and still pass the bill, hoped for a vote as early as Saturday but were watching for possible Republican delay tactics and cautious about intra-party tensions on the issue of abortion.
By 2pm, Obama's allies had prevailed easily in a pair of procedural votes after several hours of often raucous debate, but the margin was expected to tighten.
Republicans appealed to swing-vote Democrats from battleground districts to reject what they warned would end up being a costly government takeover of health care, stoking traditionally American suspicions of the public sector.
But Republican opposition was hardly the only hurdle: Democrats were wrestling with a bitterly divisive intra-party feud over whether government funds could go even indirectly to funding abortions.
Existing US law forbids federal money from going directly to abortion providers except in cases of rape or incest, or when pregnancy endangers the life of the mother, but a group of about 40 swing-vote Democrats successfully pushed for a vote on an amendment that would further tighten restrictions.
Reproductive rights groups and their Democratic supporters - the party's majority - opposed the new curbs.
Even if Democrats squeeze an overall health care bill through the House, it must still clear the Senate, where Democratic Majority Leader Harry Reid faces more daunting obstacles and has hinted any action could slip to 2010.
That would put the issue front-and-centre in the 2010 mid-term elections, when one third of the Senate, the entire House of Representatives, and many US governorships are up for grabs.
The United States is the world's richest nation but the only industrialised democracy that does not ensure that all of its citizens have health care coverage, with an estimated 36 million Americans uninsured.
And Washington spends vastly more on health care - both per person and as a share of national income as measured by Gross Domestic Product - than other industrialised democracies, according to the Organisation for Economic Cooperation and Development.
The United States spent about $US7,290 ($A7,999) per person in 2007, more than double what Britain, France and Germany spent, with no meaningful edge in the quality of care, and lags behind OECD averages in key indicators like life expectancy and infant mortality.
Under the White House-backed bill, Americans would have to buy insurance and most employers would have to offer coverage to their workers - though some small businesses would be exempt and the government would offer subsidies.
The measure includes a government-backed insurance plan, popularly known as a "public option," to compete with the private insurance industry.
