His lawyers were basing their request on a February 5th non-binding legal opinion of the UN Working Group on Arbitrary Detention, which said Assange's confinement amounted to an arbitrary detention by Sweden and Britain.
"I think (the opinion of the UN working group) is an important fact and should be taken into account," Tomas Olsson, a lawyer for Assange, told the AFP news agency.
"We want them to retry the decision and overrule it," he said.
The 44-year-old Australian sought refuge in the Ecuadorian embassy in London in June 2012 after exhausting all his legal options in Britain against extradition to Sweden over his alleged sex crimes, which he has denied.
Appeals to have the warrant dropped were also denied.
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Swedish authorities want to speak to Assange about the rape allegation dating back to 2010 and whose statute of limitations does not expire until 2020.
Assange has lived at the embassy since 2012, in a small office room with a bed, computer, sun lamp, treadmill and access to a small balcony decorated with Ecuador's flag.
He fears that if he were sent to Sweden, he could be extradited to the United States to be tried over the publication of hundreds of thousands of classified documents.
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WikiLeaks filed a complaint against Sweden and Britain to the UN working group in September 2014, claiming his confiement in the embassy was unlawful.
Both Sweden and Britain have angrily disputed the group's findings.
Founded by Assange in 2006, WikiLeaks has infuriated the United States by releasing some 500,000 secret military files on the wars in Afghanistan and Iraq and 250,000 diplomatic cables.