Julian Assange set to be released from prison after plea deal, US ...

WikiLeaks says its founder, Julian Assange, has been released from a British prison and has flown out of the United Kingdom.

WikiLeaks announced Mr Assange's whereabouts shortly after court documents showed he was due to plead guilty this week to violating US espionage law, in a deal that would allow him to return home to Australia.

Mr Assange is due to be sentenced to 62 months of time already served at a hearing on the island of Saipan.

He is expected to return home after that hearing.

A lawyer for Mr Assange did not immediately respond to a request for comment.

A filing from the US Department of Justice describes a plea deal regarding WikiLeaks founder Julian Assange.(Reuters: US Department of Justice)

WikiLeaks posted a statement on social media platform X saying Mr Assange was free and had left the UK on Monday morning local time.

Part of the statement read: "This is the result of a global campaign that spanned grassroots organisers, press freedom campaigners, legislators and leaders from across the political spectrum, all the way to the United Nations.

"This created the space for a long period of negotiations with the US Department of Justice, leading to a deal that has not yet been formally finalised."

Christine Assange, Mr Assange's mother, said she was grateful her son's ordeal had finally come to an end.

"I am grateful that my son's ordeal is finally coming to an end. This shows the importance and power of quiet diplomacy.

"Many have used my son's situation to push their own agendas, so I am grateful to those unseen, hard-working people who put Julian's welfare first.

"The past 14 years have obviously taken a toll on me as a mother, so I wish to thank you in advance for respecting my privacy."

Mr Assange's father, John Shipton, told ABC Victorian Mornings his son had spent 15 of his most productive years "in some form of incarceration or another".

"The appearances are that Julian will be able to enjoy ordinary life with his family and his wife, Stella, that's my understanding," he said of the reported deal.

"It looks as though Julian will be free to come back to Australia and my thanks and congratulations to all his supporters in Australia that have made that possible, and of course, Prime Minister Anthony Albanese."

A government spokesperson said they were aware legal proceedings had been scheduled.

"We are aware Australian citizen Mr Julian Assange has legal proceedings scheduled in the United States," a spokesperson said.

"Given those proceedings are ongoing, it is not appropriate to provide further comment.

"The Australian government continues to provide consular assistance to Mr Assange.

"Prime Minister Albanese has been clear — Mr Assange's case has dragged on for too long and there is nothing to be gained by his continued incarceration."

Filings in the US District Court for the Northern Mariana Islands show that US prosecutors have filed criminal paperwork against Mr Assange that is typically a preliminary step before a plea deal.

The paperwork outlines a single criminal count of conspiring to obtain and disclose classified US national defence documents.

In 2010, WikiLeaks released hundreds of thousands of classified US military documents relating to the wars in Afghanistan and Iraq, along with thousands of diplomatic cables.

The release was the largest security breach of its kind in US military history.

Mr Assange was indicted over the release of the information during former president Donald Trump's administration.

The secret documents were leaked by Chelsea Manning, a former US military intelligence analyst who was also prosecuted under the Espionage Act.

The trove of more than 700,000 documents included diplomatic cables and battlefield accounts, such as a 2007 video of a US Apache helicopter firing at suspected insurgents in Iraq, killing a dozen people including two Reuters news staff.

That video was released in 2010.

The charges against Mr Assange sparked outrage among his many global supporters, who have long argued that he, as the publisher of WikiLeaks, should not face charges typically used against federal government employees who steal or leak information.

Many press freedom advocates have argued that criminally charging Mr Assange represents a threat to free speech.

ABC/wires