Washington DC - President Joe Biden has said the US is "considering" dropping the prosecution of Julian Assange, as supporters of the WikiLeaks founder mark the fifth anniversary of him being held in prison in London.

Assange faces prosecution in the US over an alleged conspiracy to obtain and disclose national defense information, after the publication of hundreds of thousands of leaked documents relating to the Afghanistan and Iraq wars.

He is embroiled in a lengthy legal battle to avoid being extradited.

Biden told reporters at the White House on Wednesday: "We're considering it," when asked about a request from the Australian government to drop the prosecution.

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Assange was taken to Belmarsh prison in London five years ago, after being dragged out of the Ecuadorian embassy, where he stayed while fighting being taken to the US. His lawyers say his life would be at risk if he were extradited.

Events will be held around the world on Thursday as Assange's family and supporters continue to campaign for his release.

The editor-in-chief of WikiLeaks, Kristinn Hrafnsson, said it was not too late to halt Assange's extradition to the US.

"The campaign to free Julian Assange is supported by the Australian government, the world's leading human rights and journalists' organizations, global world leaders, and the Pope," he said.

"It is not too late for President Biden to stop Julian's extradition to the US, which was a politically motivated act by his predecessor."

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"By dropping the charges against Julian he will be protecting freedom of expression and the rights of journalists and publishers globally."

"We urge him to end this legal process, to free Julian and to recognize that journalism is not a crime."

Australian Prime Minister Anthony Albanese has been pressing for Assange's release for the past few months.

Assange is waiting to hear if he can launch a final appeal against extradition.

Biden's comment was described as "encouraging" by Assange's lawyer.