Megaupload tycoon Kim Dotcom says he is willing to go the United States to clear his name as he is at the centre of an investigation into online piracy.

The founder of the file-sharing site has challenged the US Federal Bureau of Investigation to a fair trial, and said he will face court if certain conditions are met.

The FBI claims that Dotcom led a group that has netted $175 million since 2005 by copying and distributing music, movies and copyrighted content without permission.

His lawyers says the company was simply offering online storage.

The New Zealand High Court has already ruled that search warrants used by police to search Dotcom's mansion to collect evidence were illegal. The court also said that the FBI was not allowed to send evidence to the US.

The German national and three others were arrested and he was in custody for a month before being granted bail.

The flamboyant 38-year-old is now allowed back into his mansion giving him access to hundreds of thousands of dollars for living and legal expenses.

Dotcom told a local paper that US authorities already know they cannot win the case against him, but his legal bills are mounting up into "millions of dollars", which he cannot pay because of a freeze on much of his fortune and assets.

"They just want to hang me out to dry and wait until there is no support left."