Quito (AFP) - Ecuador's efforts to negotiate the release of WikiLeaks founder Julian Assange from its London embassy have failed, the South American country's foreign minister admitted Friday.

"On the issue of mediation, I have to say very honestly that it has not been successful because two parties are needed to mediate. Ecuador is willing, by not necessarily the other party," said Foreign Minister Maria Fernanda Espinosa, referring to Britain.

But she said her country would "continue looking for mechanisms, ways" to try to solve the standoff.

Assange last week lost his legal battle to overturn an English arrest warrant against him, and with it his hopes of freely leaving the embassy, where he has been holed up since 2012.

A judge at a court in London rejected the argument of Assange's lawyers that upholding an arrest warrant was no longer in the public interest, saying "arrest is a proportionate response."

Assange was awaiting extradition to Sweden over a 2010 investigation into claims of rape and sexual assault when he breached his bail conditions to seek refuge in the embassy.

Sweden dropped its investigation last year, but the British warrant for his arrest for jumping bail remains, meaning he would be detained if he stepped outside.

The 46-year old Australian only rarely emerges onto the embassy balcony, citing concerns for his personal safety, but he frequently takes part in media conferences and campaigns via video link.

Ecuador in December granted citizenship to Assange, and asked Britain to recognize him as a diplomat in an unsuccessful attempt to provide him with the immunity that could see him walk free.

London swiftly rejected the move.