WikiLeaks founder Julian Assange has said he will turn himself over to British police on Friday if a UN panel rules he has not been arbitrarily detained, after spending more than three years in the Ecuadorian embassy in London.

"Should the UN announce tomorrow that I have lost my case against the United Kingdom 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," he said in a statement Thursday.

"However, should I prevail and the state parties be found to have acted unlawfully, I expect the immediate return of my passport and the termination of further attempts to arrest me."

Assange has been holed up in the Ecuadorian embassy in west London since 2012 in a bid to avoid extradition to Sweden over rape allegations, charges he has denied.

Ecuador has granted him asylum, but he faces immediate arrest if he steps onto British soil and for years police have been posted around the clock outside its doors at a cost of millions of pounds.

Separately, the Australian fears he could eventually face extradition to the United States to be put on a trial over the leak of hundreds of thousands of classified military and diplomatic documents by his anti-secrecy group Wikileaks.

Assange founded Wikileaks in 2006, and its 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 United States.

The main source of the leaks, US Army soldier Chelsea Manning, was sentenced to 35 years in prison for breaches of the Espionage Act.

WikiLeaks has said Sweden's handling of his case has left a "black stain" on the country's human rights record.

In September 2014, Assange filed a complaint against Sweden and Britain to the UN Working Group on Arbitrary Detention claiming his confinement in the embassy amounts to illegal detention.

"The only protection he has... is to stay in the confines of the embassy; the only way for Mr Assange to enjoy his right to asylum is to be in detention," the submission said.

"This is not a legally acceptable choice," it added, according to a file posted on the website justice4assange.com.

Any decision by the UN group would not be legally binding, but Justice for Assange claims its rulings influenced the release from detention of prominent figures including Myanmar's Aung San Suu Kyi and Washington Post journalist Jason Rezaian, who was held by Iran for 18 months.

A divisive figure, Assange has likened his confinement in the embassy, where he lives in a small room divided into an office and a living area, to living in a space station.

Previously he lived in the more impressive surroundings of an English country mansion owned by one of his supporters, documentary maker Vaughan Smith.

Source: AFP