LONDON - WikiLeaks founder Julian Assange's last-ditch legal challenge to stop his extradition from Britain to the United States is a matter of life or death, his wife Stella said on Thursday.

Assange, 52, is wanted by U.S. authorities on 18 counts relating to WikiLeaks' release of vast troves of confidential U.S. military records and diplomatic cables.

Britain approved his extradition in 2022, a decision which Assange's lawyers will fight to try and overturn next week at London's High Court.

Speaking at a media briefing on Thursday, Stella Assange said her husband would not survive if he went to the U.S..

"His health is in decline, physically and mentally," she said. "His life is at risk every single day he stays in prison – and if he is extradited he will die."

In January 2021, a judge ruled Assange should not be extradited as his mental health meant he would be at risk of suicide if held in a maximum security prison.

The High Court reversed that decision after an appeal by U.S. authorities who gave a series of assurances about Assange's treatment.

Stella Assange said they would apply to the European Court of Human Rights for an injunction if his attempt to challenge his extradition at next week's hearing in London fails.

WikiLeaks first came to prominence in 2010 when it released hundreds of thousands of classified files and diplomatic cables.

U.S. prosecutors say the leaks imperilled the lives of their agents, but Assange's supporters argue he has been victimised for exposing U.S. wrongdoing.

Assange spent seven years holed up in Ecuador's embassy in London before he was dragged out and jailed in 2019 for breaching bail conditions.

He has been held in a maximum-security prison in London ever since while his extradition case is decided.

Asked about the couple's two children, Stella Assange said they did not know about the extradition fight: "Julian and I protect the children." REUTERS