London: Lawyers for Julian Assange say they will argue that the WikiLeaks founder cannot be sent from Britain to the United States to face spying charges because a treaty between the two countries bans extradition for political offences.

Assange, 48, faces 18 counts in the US including conspiring to hack government computers and violating an espionage law. He could spend decades in prison if convicted.

Julian Assange pictured in May being taken from court. Credit:AP

The Australian appeared via videolink in Westminster Magistrates Court in London on Thursday, London time, for a case management hearing.

Assange sniffled as he sat unshaven and wearing glasses, a white shirt and a mauve jumper.