(Recasts headline, adds defence of Assange)

By Michael Holden

LONDON, Feb 24 (Reuters) - A British court begins hearings on Monday to decide whether Julian Assange should be extradited to the United States almost a decade after his WikiLeaks website enraged Washington by leaking secret U.S. documents.

A hero to admirers who say he has exposed abuses of power, Assange is cast by critics as a dangerous enemy of the state who has undermined Western security. He says the extradition is politically motivated by those embarrassed by his revelations.

The 48-year-old is wanted by the United States on 18 criminal counts of conspiring to hack government computers and violating an espionage law and could spend decades in prison if convicted.

Now, some 10 months after he was dragged from the Ecuadorean embassy where he had been holed up for seven years, Judge Vanessa Baraitser will hear arguments as to why he should or should not be sent to the United States.

Jennifer Robinson, Assange's lawyer, says his case could lead to criminalising activities crucial to investigative journalists and his work has shed an unprecedented light on how the United States conducted its wars in Iraq and Afghanistan.

"We are talking about collateral murder, evidence of war crimes," she said. "They are a remarkable resource for those of us seeking to hold governments to account for abuses."

WikiLeaks angered Washington by publishing hundreds of thousands of secret U.S. diplomatic cables that laid bare critical U.S. appraisals of world leaders, from Russian President Vladimir Putin to members of the Saudi royal family.

Assange made international headlines in 2010 when WikiLeaks published a classified U.S. military video showing a 2007 attack by Apache helicopters in Baghdad that killed a dozen people, including two Reuters news staff.

PARDON DEAL?

The hearing at London's Woolwich Crown Court will not decide if Assange is guilty of any wrongdoing, but whether the extradition request meets the requirements set out under a 2003 UK-U.S. treaty, which critics say is stacked in favour of the United States.

Baraitser has agreed that the case will get under way before being postponed until May 18, when it will resume again for a further three weeks to allow both sides more time to gather evidence.

Assange's lawyers have said in preliminary hearings that they would argue he was being sought for political offences and that the treaty banned extradition on those grounds.

Other arguments would feature medical evidence, public denunciations by leading U.S. political figures and details from the case of Chelsea Manning, an ex-intelligence analyst who was convicted by a U.S. Army court-martial in 2013 of espionage and other offences for leaking secret cables to WikiLeaks.

In 2012, Assange took refuge in Ecuador's London embassy to avoid extradition to Sweden where he was accused of sex crimes, which he denied and which were later dropped, saying he feared he would ultimately be sent on to the United States.

After seven years, he was dragged from the embassy in 2019 and then jailed for 50 weeks for skipping bail. He has remained in prison ever since, after the United States launched its extradition request.

If the judge decides Assange should be extradited, the decision needs to be rubber-stamped by Home Secretary (interior minister) Priti Patel. He would also have the right to appeal to London's High Court and then possibly to the Supreme Court, Britain's top judicial body. (Editing by Guy Faulconbridge)

Our Standards: The Thomson Reuters Trust Principles.