An American lawyer for Kim Dotcom believes his client's extradition hearing will be delayed again, as the FBI appeals against every ruling made in the New Zealand courts.
The internet entrepreneur and co-founder of the file-sharing site Megaupload is facing copyright, money laundering and fraud charges.
Mr Dotcom was at the Court of Appeal for the first time on Thursday, as Crown lawyers acting for US authorities appealed against a High Court ruling ordering that the FBI hand over copies of evidence it plans to use against him.
The court has reserved its decision.
Mr Dotcom's US-based lawyer Ira Rothken was in Wellington for the hearing and says he is "cautiously optimistic" about the outcome.
However, as there are still several other matters before the courts, Mr Rothken believes the extradition hearing - already delayed once - will be put off again.
Kim Dotcom says the action being taken by the US is wrong. He believes it is a political attack on his business and has no legal grounds.
Megaupload was indicted in a US federal court in Virginia on 19 January this year and the site was shut down. Mr Dotcom and three co-accused were arrested in Auckland, where he lives, the following day.
Formal papers requesting their extradition were lodged by the US in March.