Jessica Estepa, and Jane Onyanga-Omara

USA TODAY

LONDON — WikiLeaks founder Julian Assange said Thursday that he would allow British police to arrest him if a United Nations panel rules Friday against him in a non-binding legal case about his detention in London.

Assange has been holed up in Ecuador's Embassy since June 2012. If he steps outside, he would immediately be arrested and face extradition to Sweden and the United States.

"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," the Australian national wrote in a statement released on Twitter.

The United Nations Working Group on Arbitrary Detention is expected to announce Friday its verdict on whether Assange is being detained illegally. The decision comes more than 16 months after he filed a complaint with the panel about his detention.

Sweden’s foreign ministry said Thursday that the panel had concluded that Assange had been "arbitrarily detained." A U.N. official said Sweden was informed of the decision on Jan. 22, the Associated Press reported. The U.N. said it would not release any information on the decision prior to Friday's announcement.

The panel has previously ruled on whether a person's imprisonment or detention is lawful, leading to releases, the Sydney Morning Herald reported.

Assange noted that if the panel rules in his favor, he expects the return of his passport and "the termination of further attempts to arrest me."

Sweden drops part of Assange sex assault charges

But Scotland Yard said that if Assange leaves the embassy, its officers "will make every effort to arrest him."

Britain's Foreign Office said in a statement Thursday: “We have been consistently clear that Mr. Assange has never been arbitrarily detained by the U.K. but is, in fact, voluntarily avoiding lawful arrest by choosing to remain in the Ecuadorean embassy. An allegation of rape is still outstanding and a European Arrest Warrant in place, so the U.K. continues to have a legal obligation to extradite Mr. Assange to Sweden.”

Sweden sought extradition because Assange is accused of being involved with a suspected rape. Assange had faced three other sexual assault charges in the country, but they expired in August because of the statute of limitations.

The U.S. Justice Department has sought Assange's extradition in order to charge him with espionage related to WikiLeaks' publication of thousands of diplomatic letters.

Estepa reported from McLean, Va.