Federal MPs from across the Australian political spectrum have united to call on the US government to end its ongoing pursuit of WikiLeaks founder Julian Assange.

Former Nationals leader Barnaby Joyce, Labor MP Tony Zappia, teal independent Monique Ryan, Liberal senator Alex Antic and two Greens senators Peter Whish-Wilson and David Shoebridge are in Washington DC to lobby the government to abandon its extradition proceedings against Assange.

The Wikileaks founder is facing historic allegations of espionage.

The delegation has scored a number of meetings, with Mr Joyce saying the trip was going well.

“We just continue to do the best job we can,” he said from Washington.

The delegation had been clear in meetings that there was “a powerful expectation” that Assange be able to come home and be with his family before Christmas, Senator Shoebridge said.

It was imperative that the matter moved forward, Republican congressman Thomas Massie said.

“The precedent this case sets – to put someone in prison or extradite them for merely publishing facts – is very dangerous,” he said.

US authorities were listening to the concerns of the Australian delegation as Assange’s health continues to deteriorate, his brother Gabriel Shipton said.

“They’re taking these meetings and listening to what these politicians have to say, which is real progress in terms of the campaign to free Julian,” Mr Shipton told Sky News.

“These are really tough times for Julian – with this extradition looming over his head, four and a half years in a maximum security prison, he’s not doing well.”

Foreign Minister Penny Wong reiterated the government’s position that it would like to see the case come to an end.

“We are consistent in our view that we think this has gone on too long,” she told reporters on the sidelines of the UN General Assembly in New York.

“The breadth of political representation on this delegation, I think, demonstrates that there are a great many people in Australia who would like to see this matter resolved.”

Assange and his legal team needed to be a part of the resolution and that remained a matter for them, she added.

The Australian delegation took out a full-page advertisement in the Washington Post about Assange, which was signed by more than 60 Australians politicians, including independents and members from the Liberals, Labor and the Greens.

The prosecution served no purpose and was unjust, the ad said.

Assange, an Australian citizen, faces 17 charges of espionage and one charge of computer misuse after WikiLeaks published a raft of classified documents more than a decade ago.

They included videos of a 2007 Baghdad air strike, field reports from the Iraq War, and hundreds of thousands of items of US diplomatic correspondence

Assange was granted political asylum and lived in London’s Ecuadorian embassy from 2012 until 2019.

He has been imprisoned in the United Kingdom for the four years since then and continues to fight extradition to the US.

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.

Mr Joyce said the delegation was not trying to pick a fight with the government but represent the views of Australians.

The delegation will meet members of Congress and Senate, the US State Department and the Department of Justice.

The prime minister and opposition leader in May publicly agreed Assange’s prosecution had gone on for too long.

Anthony Albanese is set to meet President Joe Biden at the White House on an official state visit in October.

Diplomats needed to ensure a resolution before then so “the Americans don’t embarrass our prime minister”, Mr Shipton said.

– AAP