By Tess Ikonomou, Dominic Giannini, Kat Wong and Jacob Shteyman in Canberra

Julian Assange has arrived in Thailand after being freed from a British jail, as his grateful mother says the decades-long ordeal is almost over.

The Wikileaks founder, 52, has been fighting extradition to the US over espionage charges for obtaining and publishing classified information.

But on Tuesday, Australian time, he agreed to plead guilty as part of a deal with US prosecutors, ending his imprisonment in the notorious Belmarsh prison and paving the way to return to Australia.

Assange’s mother Christine Assange said his release 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,” she said.

“The past 14 years has obviously taken a toll on me as a mother.”

Assange’s wife Stella was elated, expressing gratitude to his supporters in a social media post that included video of him boarding a flight out of the UK.

His plane touched down in Bangkok at 3.30pm, Sydney time, from where it was scheduled to fly on to the Northern Mariana Islands.

He is due to be sentenced at a District Court hearing on Saipan, the capital of the US Pacific territory, at 9am on Wednesday.

Assange agreed to plead guilty to a single criminal count of conspiring to obtain and disclose classified US national defence documents, according to filings in the US District Court for the Northern Mariana Islands.

Wikileaks, the website Assange created in 2006, announced the deal on Tuesday in a social media post.

Assange “paid severely” for holding the powerful accountable for their actions and upholding the people’s right to know, the organisation wrote on X, formerly Twitter.

Australia has long called for the US to end its pursuit of Assange.

Prime Minister Anthony Albanese had directly raised the issue with US President Joe Biden, and in September politicians from across Australia’s political spectrum converged on Washington to lobby US decision-makers.

Mr Albanese declined to comment directly on the case during question time, citing the ongoing legal proceedings, but reiterated his desire to see his detention brought to an end.

“Regardless of the views that people have about Mr Assange’s activities, the case has dragged on for too long,” he said.

“There is nothing to be gained by his continued incarceration and we want him brought home to Australia.”

Opposition foreign affairs spokesman Simon Birmingham, Greens senator David Shoebridge and Nationals senator Matt Canavan welcomed the decision.

But caution was urged by Nationals MP Barnaby Joyce, an outspoken Assange supporter who took part in the Washington delegation.

“We’re in the process of a 1500-metre race. We don’t stop and start waving at the crowd on two-and-a-half laps, we wait to the end of the race,” he said.

In April at the White House, President Biden told reporters he was considering Australia’s request to drop the charges.

Prosecutors wanted to put Assange on trial for publishing military documents about the war in Afghanistan and Iraq, which authorities said had damaged national security and endangered the lives of US agents.

Assange was arrested in the UK in 2010 on a separate matter and took refuge in Ecuador’s embassy in London. He was taken from the embassy and sent to Belmarsh prison in 2019.