A US bid to extradite Megaupload boss Kim Dotcom from New Zealand for alleged online piracy has been delayed until at least November, court officials said Monday.

The extradition case, launched after Dotcom was arrested in an armed raid on his Auckland mansion in January 2012, has been repeatedly rescheduled amid legal wrangling over evidence disclosure.

A spokeswoman for Auckland's North Shore District Court said the extradition would no longer be heard in August as planned, but had been pushed back to November 21.

She said a back-up date of April 14, 2014 has also been reserved in case there were more delays in the case, which had become increasingly complex amid numerous legal hearings and challenges since Dotcom's arrest.

The US Justice Department and FBI allege Dotcom's Megaupload sites netted more than $175 million in criminal proceeds and cost copyright owners more than $500 million by offering pirated copies of movies, TV shows and other content.

The Megaupload empire, which at its peak had 50 million daily visitors and accounted for four percent of all Internet traffic, was shut down after the raid, although Dotcom has since launched a similar service called Mega.

He remains free on bail in New Zealand and denies the US charges of racketeering, fraud, money laundering and copyright theft, which could see him jailed for up to 20 years if convicted.

The German national has scored a number of legal victories in his case, including a ruling that the raid on his mansion was unlawful and an admission that New Zealand's intelligence agency illegally spied on him before his arrest.

The High Court last month ordered police to return any digital material seized in the raid that was not directly related to the prosecution case.

Dotcom is also fighting a separate case in the Supreme Court to force police to hand over all the evidence they hold against him, arguing he cannot mount an effective defence against extradition without it.