A UN panel has ruled that Julian Assange had been "arbitrarily detained" by Sweden and Britain, stoking the hopes of the Wikileaks founder that he could walk free after almost four years in Ecuador's London embassy.
The panel added that Assange should be able to claim compensation from Britain and Sweden over his time in the embassy, where he sought refuge and has lived since with no access to outdoor space and little sunlight.
The 44-year-old Australian hopes that the panel's ruling, although non-binding, will put pressure on British and Swedish authorities to drop attempts to arrest him.
In a statement, the panel said it had adopted an opinion "in which it considered that Mr. Julian Assange was arbitrarily detained by the Governments of Sweden and the United Kingdom of Great Britain and Northern Ireland."
It added: "The working group also considered that the detention should be brought to an end and that Mr. Assange should be afforded the right to compensation."
In a statement Thursday, Assange had promised to "exit the embassy at noon on Friday to accept arrest by British police" if the panel ruled against him.
He added that a ruling in his favour should lead to "the immediate return [of] my passport and the termination of further attempts to arrest me".
Assange's lawyers are set to hold a press conference at 1200 GMT to respond to the ruling.
Assange entered the embassy, near Harrods department store in London's exclusive Knightsbridge district, to avoid the threat of arrest and extradition.
Swedish authorities want to speak to him about a rape allegation whose statute of limitations does not expire until 2020.
But he fears that he could then be sent to the US and face prison there if he gave himself up for questioning.
Wikileaks' activities -- including the release of 500,000 secret military files on the wars in Afghanistan and Iraq and 250,000 diplomatic cables -- have infuriated the US.
The main source of the leaks, US Army soldier Chelsea Manning, was sentenced to 35 years in prison for breaches of the Espionage Act.
Swedish prosecutors have said that the UN panel's opinion "has no formal significance for the ongoing investigation under Swedish law."
- Years of wrangling -
A hero to some and a dangerous egocentric to detractors, the computer programmer and hacker founded anti-secrecy group WikiLeaks in 2006.
Ecuador granted Assange asylum in 2012, and on Thursday President Rafael Correa told a news conference the expected UN decision "shows we were right, after so many years".
Britain has spent millions of pounds maintaining a 24-hour guard outside the embassy to immediately arrest Assange if he set foot on British soil.
The guard was withdrawn last year, but police said they would strengthen a "covert plan" to prevent Assange slipping away.
The decision by the UN panel follows a complaint by WikiLeaks against Sweden and Britain in September 2014 in which they claimed Assange's confinement in the embassy was unlawful and that he was a "political refugee".
"This is an application framed by political events, but at its heart, it is about a person who has been deprived of his liberty in an arbitrary manner for an unacceptable length of time," their submission read.
Though the panel's rulings are not legally binding, the Justice for Assange support group said it had influenced the release of prominent figures including Myanmar's Aung San Suu Kyi and former Maldives president Mohamed Nasheed.
The British government has denied that Assange was ever arbitrarily detained and said he was rather "voluntarily avoiding lawful arrest".
"An allegation of rape is still outstanding and a European Arrest Warrant in place, so the UK continues to have a legal obligation to extradite Mr Assange to Sweden," a spokesman said.