British police have insisted WikiLeaks founder Julian Assange will be arrested if he steps outside the Ecuadorian embassy, where he has been holed up for more than three years.
A United Nations panel is on Friday expected to reveal its ruling that Mr Assange has been "arbitrarily detained" in the embassy, which he entered in 2012 to avoid being extradited to Sweden over sexual assault allegations.
Sweden's Foreign Ministry has confirmed reports on Thursday that the panel has ruled in the 44-year-old Australian's favour.
The British government has declined to comment, but a spokesman for Prime Minister David Cameron says the UN findings are not "legally binding".
"There is a European arrest warrant currently in place and we have a legal obligation to put that into effect," he said.
"(Mr Assange) has never been detained in this country, so there is no arbitrary detention. He is avoiding lawful arrest by choosing to remain in the Ecuadorian embassy," he continued.
In a statement via WikiLeaks on Thursday, Mr Assange said that if he lost his unlawful detention case against the UK and Sweden, "I shall exit the embassy at noon on Friday to accept arrest by British police as there is no meaningful prospect of further appeal".
If Mr Assange does succeed in the UN claim and his detention is deemed unlawful, he said he expected the immediate return of his passport and an end to attempts to arrest him.
Speaking in London, Foreign Minister Julie Bishop said she would keep a "watching brief" on the affair, but added that Mr Assange had not sought consular assistance from Australia for years.
The cyber-activist has been living in the embassy in central London since June 2012, when the Ecuadorian government granted him asylum.
He said he feared that if he was extradited to Sweden he could be transported on to the US to face charges over the leaking of hundreds of thousands of classified documents.
Three allegations of sexual assault in Sweden were dropped against Mr Assange last year when they reached their five-year statute of limitations.
However, Swedish prosecutors still want to question him over a 2010 rape allegation.
Mr Assange has denied all of the accusations
Per Samuelson, one of Assange's Swedish lawyers, said if the UN panel judged Assange's time in the embassy to be custody, he should be released immediately.
"It is a very important body that would be then saying that Sweden's actions are inconsistent with the European Convention on Human Rights. And it is international common practice to follow those decisions," Samuelson told Reuters.
Since Assange's confinement, WikiLeaks has continued to publish documents on topics such as the Trans-Pacific Partnership, one of the world's biggest multinational trade deals, which was signed by 12 member nations on Thursday in New Zealand.
