FIGHTING: Kim Dotcom and his co-accused are taking on the US government.

The size of Kim Dotcom's Megaupload servers has made disclosing the evidence against him near impossible in the allotted time, New Zealand Crown lawyers have argued.

A District Court judge last week overruled the US Government and granted the internet millionaire the right to information gathered by the FBI in the copyright case against him.

The Crown has today argued against the order in the High Court at Auckland, saying it was "unrealistic" to do so in the 21 days allowed by the court.

Fergus Sinclair, for the Crown, said the servers Megaupload used were massive and would have to be disclosed as the FBI had copied them.

Megaupload had 18 servers with a company called Cogent but they were so large the FBI could copy only two of them, he said.

"It's simply too big a job. They wouldn't get a small way through it in that time."

Dotcom's lawyer William Akel said there was a concern US authorities could make the matter take "as long as they say it could take".

Justice Helen Winkelmann reserved her decision.

Dotcom, 38, is currently on bail awaiting an extradition hearing.

Authorities say he and his three co-accused - Mathias Ortmann, Fin Batato and Bram Van der Kolk - used Megaupload and its affiliated sites to knowingly make money from pirated movies and games.

Dotcom is charged with multiple copyright offences.