WikiLeaks founder Julian Assange has announced he will hand himself over to authorities if he loses a case before the United Nations.

In a statement via WikiLeaks on Thursday, Mr Assange said that if he loses 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”.

However, if Mr Assange succeeds in the UN claim and his detention is deemed unlawful, he said, he expects the immediate return of his passport and an end to attempts to arrest him.

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The UN’s Working Group on Arbitrary Detention is expected to release on Friday its decision on whether Mr Assange’s three-year-plus refuge in the Ecuadorian embassy constitutes unlawful detention.

The Australian-born cyber-activist has been living in the Ecuadorian embassy in central London since June 2012 when the Ecuadorian government granted him asylum due to his fear of extradition to the United States for the release of sensitive information.

Mr Assange also faces extradition to Sweden for questioning in relation to a 2010 sexual assault investigation in which he has denied responsibility.

The UK government has threatened to arrest him if he leaves the embassy.

In his application to the UN body, Mr Assange argued that his situation constitutes a deprivation of liberty because he is forced to choose between being confined or forfeiting his right to political asylum.

The application says he has been confined in an area of 30sq metres with no access to fresh air or sunlight for 816 days, while his communications are restricted or interfered with and he has no access to adequate medical facilities.

It notes he has not been charged with any offence.

The five members of the Working Group on Arbitrary Detention are academics and experts in international law and human rights and include Australian Leigh Toomey, a former member of Australia’s delegation to the UN General Assembly.

Mr Assange and WikiLeaks came to global prominence in 2010 with the release of the Collateral Murder video – footage of people being killed by a US military helicopter in Iraq.