WikiLeaks founder Julian Assange appealed to Britain's Supreme Court on Wednesday not to extradite him to Sweden over accusations of sex crimes, a move that could push his anti-secrecy website further towards oblivion.

Australian-born Assange, 40, became a worldwide celebrity and infuriated the U.S. government in 2010 when WikiLeaks released secret video footage and thousands of U.S. diplomatic cables about the wars in Iraq and Afghanistan.

Since then, the scoops have dried up and WikiLeaks has faded from the news headlines, starved of cash by major credit card companies that are refusing to process online donations to it, and bogged down by Assange's protracted legal troubles.

Assange was detained in Britain in December 2010 on a European arrest warrant issued by a Swedish prosecutor after two female former WikiLeaks volunteers accused him of sexual assault.

His lawyers argue that the warrant is invalid because it was issued by a prosecutor rather than a neutral judge or court. He has not been charged in Sweden but is wanted for questioning.

If the Supreme Court in London rejects the argument, he may take his case to the European Court of Human Rights but it is unclear whether that would stop his extradition to Sweden.

HE SPEAKS TRUTH TO POWER

A small group of demonstrators gathered outside, braving a freezing morning to show support for Assange, who looked relaxed in a dark grey suit and purple tie as he entered court.

They carried banners with slogans such as The system punishes whistleblowers to protect its own and Free Assange.

He speaks truth to power. He should be considered a national hero, said Scott Albrecht, a former U.S. soldier turned peace activist.

The Supreme Court hearings will last two days and the court is expected to announce its decision some weeks later.

Assange denies any wrongdoing and has said that the sex accusations, which surfaced at the height of the international furore over WikiLeaks, were an attempt to silence him.

He is convinced that U.S. authorities are looking for a way to go after him in retaliation for WikiLeaks' revelations.

Washington is divided over Assange, with some officials calling for tough action against him to deter would-be leakers and others saying a prosecution would be legally problematic and would give him a boost when he appears headed for irrelevance.

Bradley Manning, a U.S. army intelligence analyst suspected of passing thousands of classified documents to WikiLeaks, is facing a court-martial on 22 charges including aiding the enemy and wrongfully causing intelligence to be published online.

Meanwhile, Assange has been holed up under house arrest for over a year, mostly at the English country mansion of a wealthy supporter.

In another TV first, Kremlin-funded station Russia Today announced last week that it had hired Assange to host a political talk show called The World Tomorrow.

(Editing by Mark Heinrich)