London, UK - Campaigners calling for the release of Julian Assange will stage events on Wednesday to mark the 1,000 days the WikiLeaks founder has spent in prison.

His supporters will gather outside Belmarsh Prison in London, where he is being held as the United States continues to attempt to extradite him, having won a crucial appeal in December.

His fiancée, Stella Moris, renewed her call for his release, saying Assange has spent longer in Belmarsh than many prisoners sentenced for violent crimes.

"His young children, aged two and four, have no memory of their father outside the highest security prison of the UK," Moris said.

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"Julian is simply held at the request of the US government while they continue to abuse the US-UK extradition treaty for political ends."

"The US government is trying to put an Australian publisher on trial in a US national security court, where he faces a 175-year sentence and imprisonment in conditions of torture and total isolation, simply because he was doing his job," she added.

"Because he received true information about the victims and the crimes committed by US operations in Guantanamo Bay, Afghanistan, and Iraq from Chelsea Manning, and he published it."

Moris said that as long as he remains in prison, Assange will be a political prisoner, and his "indefinite incarceration" will kill him unless it is brought to an end.

"In those 1,000 days, Julian has been held in extraordinary isolation for part of the time, faced two Covid shutdowns and, in October, he suffered a stress-induced stroke during his latest hearing," she added.

"His lawyers have complained about the limited access they have to their client which has undermined his defense. His requests to attend his own hearings have been refused, and when he has been permitted to attend, his requests to sit next to his lawyers have also been refused."

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Assange (50) has been accused of conspiring with Manning, a former US military intelligence analyst, to leak a trove of classified material in 2010.

The secret documents relating to potentially serious wrongdoing by Allied forces in Afghanistan were released on Wikileaks while Assange also collaborated with journalists at prominent news outlets.

His supporters and press freedom groups view him as an investigative reporter who has brought war crimes to light.