Stella Assange’s first visit to Australia should have been a picturesque experience, cycling in Melbourne and relaxing on Bondi Beach.

But as she felt the cool Bondi sand slip through her toes, her husband Julian continues to languish on the cold cement floors of London’s Belmarsh Prison.

For 1502 days, the WikiLeaks founder has been waiting behind bars under threat of extradition to the United States, where he faces a 175-year sentence on espionage charges for leaking classified military documents.

“If Julian is extradited, he will be buried in the deepest, darkest hole of the US prison system, isolated forever,” Ms Assange said in an emotional address to the National Press Club in Canberra on Monday.

“We must do everything we can to ensure that Julian never, ever sets foot in US prison.

“Extradition in this case is a matter of life and death.”

Ms Assange had also come to Australia to advocate for her husband’s release in the presence of US President Joe Biden, who was scheduled to be in Sydney for Quad talks before pulling out.

But Mr Biden’s non-presence has not deterred Ms Assange from coming to the country of her husband’s birth because she believes Australia has a crucial role to play in securing his release.

“Australia is the United States’ most important ally,” she said.

“Julian’s life is in the hands of the Australian government.”

Assange’s Australian supporters are hopeful Prime Minister Anthony Albanese will continue to plead his case after meeting with President Biden during G7 talks in Japan at the weekend.

Support in Australia is growing, with Mr Albanese and Opposition Leader Peter Dutton in agreement that Assange has been incarcerated for too long.

“Nothing is served on the ongoing incarceration of Julian Assange,” the prime minister told parliament on Monday.

The treatment of Assange, his wife argues, has emboldened authoritarian regimes to clamp down on press freedoms around the world.

“The case against Julian cannot be understood as anything other than an absurdity. A stupefying decision of egregious overreach,” she said.

“America’s case against Julian has created a new race to the bottom – a new normal, which makes it easier to get away with imprisoning journalists.”

As their young children grow older and come to realise their father’s plight, Ms Assange feels a sense of urgency to secure her husband’s freedom.

Jennifer Robinson, an Australian human rights lawyer on Assange’s legal team, did not rule out attempting to strike a plea deal with US prosecutors to seal his release, potentially on time served.

But she insists Assange has committed no crime.

However, Ms Robinson welcomed a comparison to the case of terrorism-accused David Hicks, who was returned to Australia as part of a political settlement after his defence struck a plea bargain.

– AAP