US secretary of state Antony Blinken has pushed back against Australian demands for an end to Wikileaks founder Julian Assange’s prosecution – saying he is accused of “very serious criminal conduct” by publishing a trove of classified documents more than a decade ago.

Australia’s centre-left Labour Party government has been arguing since winning the election last year that the United States should end its pursuit of the 52-year-old Australian citizen, who has spent four years in a British prison fighting extradition to the US.

Assange’s freedom is widely seen as a test of Australia’s leverage with US President Joe Biden’s administration.

Mr Blinken confirmed on Saturday that Assange was discussed in annual talks with foreign minister Penny Wong in Brisbane.

“I understand the concerns and views of Australians. I think it’s very important that our friends here understand our concerns about this matter,” Mr Blinken told reporters.

“Mr Assange was charged with very serious criminal conduct in the United States in connection with his alleged role in one of the largest compromises of classified information in the history of our country.”

Ms Wong said Assange’s prosecution has “dragged for too long” and Australia wants the charges “brought to a conclusion”.

Australia remains ambiguous about whether the US should drop the prosecution or strike a plea deal.

US secretary of state Antony Blinken
US secretary of state Antony Blinken (Manuel Balce Ceneta/AP)

Assange faces 17 charges of espionage and one charge of computer misuse over WikiLeaks’ publication of hundreds of thousands of classified diplomatic and military documents in 2010.American prosecutors allege he helped US army intelligence analyst Chelsea Manning steal classified diplomatic cables and military files that WikiLeaks later published, putting lives at risk.

Australia says there is a “disconnect” between the US treatment of Assange and Manning.

Then-US president Barack Obama commuted Manning’s 35-year sentence to seven years, which allowed her release in 2017.