Multi-millionaire Kim Dotcom has offered a deal to the United States government, saying he'll go voluntarily to the US to defend the internet piracy case against him.

The German-born Megaupload founder, who is on bail in Coatesville, north of Auckland, took to Twitter to extend the offer to the US Department of Justice.

"Hey DOJ, we will go to the US. No need for extradition. We want bail, funds unfrozen for lawyers & living expenses," Dotcom tweeted.

The tweet followed Tuesday's news that Dotcom's extradition hearing has been deferred until March 25.

The three-week hearing had been due to get under way on August 6 at North Shore District Court.

Dotcom, who holds New Zealand residency, also reacted to the court decision on Twitter, saying "dirty delay tactics by the US" had destroyed his business and taken all his assets.

"The NZ government is refusing an NZ resident due process and a fair defense. Shame on you John Key for allowing this to happen. Shame on you."

US authorities are trying to extradite Dotcom and three others to face racketeering, copyright and money laundering charges relating to the Megaupload website. They face up to 20 years in prison if convicted.

The four were arrested in New Zealand in January in a joint operation by New Zealand authorities and the FBI.

Last week, prosecutors acting on behalf of the US government appeared in the High Court to appeal a District Court ruling that Dotcom and his co-accused must be granted access to the evidence held against them for the extradition hearing.

The outcome of that appeal is still unknown.

Late last month, a High Court ruling declared the armed police raid on Dotcom's Coatesville mansion in January illegal.

Justice Helen Winkelmann said the search warrants used were too broad and police exceeded their powers in seizing what they did.

She also said it was unlawful for copies of Dotcom's computer files to be taken by US authorities and New Zealand police should return copies to 38-year-old Dotcom.