“Journalism has been re-classed as espionage; an unprecedented prosecution has been taken against a publisher for the very first time in the more than 100-year history of this act and it is going to set a precedent … that can then be used against the rest of press anywhere in the world,” she said.

The US wants Assange to face trial on one charge of computer hacking and 17 charges of violating the 1917 Espionage Act, relating to one of the biggest leaks of classified material in history. If found guilty, Assange faces up to 175 years in jail, although authorities have said any sentence is likely to be much lower.

Prosecutors say he conspired with US Army intelligence analyst Chelsea Manning to hack into a Pentagon computer and release secret diplomatic cables and military files on the wars in Iraq and Afghanistan. The trove included 90,000 reports relating to the war in Afghanistan, 400,000 relating to the Iraq war and 250,000 US diplomatic cables. Manning’s 35-year prison sentence was commuted by then US president Barack Obama after four years.

Assange also published thousands of emails belonging to Democratic presidential candidate Hillary Clinton’s campaign chairman, a development that dominated her 2016 election campaign.

Lawyers for Assange plan to argue he can’t get a fair trial in the US, that a US-UK treaty prohibits extradition for political offences and that the crime of espionage was not meant to apply to publishers.

His lawyers believe his foreign nationality and his political opinions would make it difficult for him to get a fair trail. Also, they believe Biden may see Assange as “closer to a high-tech terrorist than a whistleblower”.

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Assange and his supporters have also argued his leaking of classified military documents should be protected under the US Constitution’s First Amendment because he was acting as a journalist when he published the documents. Those who’ve questioned the charges include the editorial boards of The New York Times and The Guardian, as well as Amnesty International.

He has been held at London’s Belmarsh jail since April 2019 when he was sentenced for skipping bail conditions. He had previously spent seven years in the Ecuadorian embassy after breaking bail in 2012 when he was due to be extradited to Sweden on unrelated sexual assault charges, which were subsequently dropped. He was arrested and forcibly removed from the Ecuadorean embassy by British police in 2019.

Stella Assange told BBC Radio 4’s Today program that “this could very well be the final hearing for Julian”.

“Julian cannot, will never be safe in a US prison, there is no question about it,” she said. “We know that there are elections coming up in the United States. He will simply never be safe if he is in US custody.”

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If the London court rejects Assange’s plea for a full appeal, he could be extradited to the US once British officials approve his removal. His legal team plans to appeal an adverse ruling to the European Court of Human Rights, but they fear he could possibly be transferred before the court in Strasbourg, France, could halt his removal.

Australia’s parliament last week passed a motion calling for Assange’s return to Australia, with Prime Minister Anthony Albanese, one of 86 MPs to vote in favour against 42 who opposed. He said he hoped the case could be “resolved amicably”.