Julian Assange is "extremely pleased" at an anticipated ruling by a United Nations panel that he has been unlawfully detained in London and plans to "call on the UK" to abide by its obligations, ITV News has learned.
Supporter and friend John Pilger told ITV News the ruling, which could lead the way for Mr Assange to potentially walk free in days, was the "first glimpse of justice" after years of "effective detention".
The Government though has said it will not pre-empt the UN panel's announcement and still supports a police plan to arrest him if he leaves the Ecuadorian embassy.
The decision by the UN working group is due to be published on Friday but, according to the BBC, it is understood it will rule in Mr Assange's favour.
Mr Pilger told ITV News the release was now a matter of international law and had "nothing to do with the Metropolitan Police".
Regarding Mr Assange's likelihood of soon leaving the embassy, Mr Pilger said: "He will wait until he gets justice but it has arrived."
Mr Assange announced he would volunteer himself to police for arrest if the UN Working Group on Arbitrary Detention ruled against him over a complaint he filed against the UK and Sweden in September 2014.
The panel's decision is expected to precede calls from the UN for the UK and Sweden to release Mr Assange.
The 44-year-old Australian - who considers himself under house arrest - said he expects to walk free if the panel announces in his favour.
The Metropolitan Police said they will still make "every effort" to arrest the WikiLeaks founder should he leave the embassy.
A Government spokesperson said it would not "pre-empt any opinions" by the UN panel but said Mr Assange has "never been arbitrarily detained by the UK" and is "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 UK continues to have a legal obligation to extradite Mr Assange to Sweden," the spokesperson added.
Mr Assange has been living in the London embassy for more than three years and has been granted political asylum by the Ecuador government.
He believes he will be transported to the United States to be questioned over the activities of WikiLeaks if he is extradited to Sweden. There is an espionage case against him in the US.
Who are the UN legal experts examining Assange's case?
The UN's Working Group on Arbitrary Detention (WGAD) was established in 1991 to investigate whether states are in compliance with human rights obligations.
It has ruled on hundreds of cases concerning international laws like the UN Declaration on Human Rights, the European Convention on Human Rights and the UN Standard Minimum Rules for the Treatment of Prisoners.
WGAD receives submissions from a complainant and respondents and decides whether the case amounts to unlawful detention.
Burmese stateswoman Aung San Suu Kyi is among a number of high profile complainants who have been supported by the group's rulings.
Julian Assange filed a complaint against Sweden and the UK on September 12 2014, with the two countries responding in November of that year.