Australian politicians are urging the government to take a stance and demand the release of WikiLeaks founder Julian Assange.

On Friday, the US government overturned a block on the extradition of Assange from Britain to face trial for publishing top-secret documents exposing war crimes perpetrated by the US and its allies across the globe, although options to appeal remain open to his legal team.

Washington presented the challenge after a lower court judge in London ruled in January that the 50-year-old journalist would be at a real and oppressive risk of suicide in the US justice system.

Assange’s lawyers said they will appeal the ruling in the UK’s supreme court.

The Australian federal independent MP Andrew Wilkie called on Prime Minister Scott Morrison to demand the release of Assange and “end this lunacy."

“Mr Assange should be looking forward to spending Christmas with his two young boys and his fiancee, but instead he’s facing a 175-year jail sentence and the very real possibility of living out his final days behind bars,” Wilkie said.

The independent MP accused the UK of being “a lackey of the United States and that Australia is delighted to go along for the ride.”

Similarly, the Greens senator Janet Rice said “foreign Minister Marise Payne must urgently speak to the US and tell them to drop these absurd charges and end Assange’s torture.”

For his part, UN's special rapporteur on torture Nils Melzer described the ruling as a "politically motivated verdict," and criticized it.

Melzer told the DPA news agency that “This is a shortcoming for the British judiciary,.” stressing that Assange “is not in a condition to be extradited.”

The decision by a London court to allow Julian Assange, the founder of Wikileaks, to be extradited to the United States is "shameful," Russian foreign ministry spokeswoman Maria Zakharova said on Friday.

Assange has been in custody since 2019, despite the fact that he had served a previous sentence over breaching bail conditions in a separate case.

He had also spent seven years at the Ecuadorian embassy in London to avoid his extradition to Sweden.