US President Joe Biden said Wednesday he was "considering" a request by Australia to drop the prosecution of WikiLeaks founder Julian Assange on espionage charges.

Australia's parliament passed a motion in February with the prime minister's support calling for an end to the legal saga surrounding Assange, who has been held in Britain since 2019 while fighting extradition to the United States.

"We're considering it," Biden replied at the White House when asked by a reporter if he had a response to Australia's request.

Biden, who took the question while walking with visiting Japanese Prime Minister Fumio Kishida to a meeting in the Oval Office, did not elaborate.

Australian citizen Assange, 52, has been indicted by the US government over his role in the 2010 leaking of a huge trove of classified documents related to the wars in Iraq and Afghanistan.

If convicted, he faces jail terms of up to 175 years.

In response to Biden's comments, Assange's wife Stella said on social platform X: "Do the right thing. Drop the charges."

She has previously said Assange's physical and mental health are in decline in jail and that her husband "will die" if sent to the United States.

Assange and his supporters say he exposed US military wrongdoing and see his case as a fight for media freedom. Washington says his leaks put lives at risk by publishing documents that included the names of intelligence sources.

- 'So brutal' -

Assange is currently waiting to learn if he can make a last-ditch appeal against extradition, after a British court last month delayed a decision on his case. It is now expected May 20.

In late March, the High Court in London gave the United States three weeks to provide further "assurances" on his treatment if he is sent there to face charges.

WikiLeaks editor-in-chief Kristinn Hrafnsson on Wednesday called for "a political solution" to Assange's plight, as supporters rallied in central London on the eve of the fifth anniversary of his arrest.

"This is a case that just should never have been started in the first place," Hrafnsson told AFP at the rally.

He said Assange's time in the high-security Belmarsh Prison in southeast London was "so excessive and so brutal."

Hrafnsson said Canberra should link the case to its landmark AUKUS security pact with Washington and London to secure Assange's release.

"They should be bold and say we have nothing to discuss unless you drop the charges against Julian Assange so he can walk free and come back to Australia," he said.

Before going to prison, Assange spent seven years in Ecuador's London embassy to avoid extradition to Sweden, where he faced accusations of sexual assault which were later dropped.

Other protests supporting Assange are expected around the world Thursday.

Campaign groups including Amnesty International and Reporters Without Borders have called for his release and denounced the prosecution under the 1917 US Espionage Act, which has never been used over the publishing of classified information.