"There is just one decision left for Julian to be extradited. If the judges decide against him on Monday there is no further right of appeal in the UK and he will be extradited," she told a press conference.

The human rights lawyer and campaigner said it was unclear how quickly the extradition would then take place. 

"We know in other cases of extradition to the US on national security grounds the person has been extradited within 24 hours of the decision being made," she said.

The High Court in London will rule on Monday whether to allow a full appeal against extradition of Julian Assange from the UK to the US.

In a ruling in March, the court found three of the 10 grounds in Assange's case against extradition valid, but asked the US authorities for further assurances.

The judges gave the US three weeks to provide "satisfactory assurances" that Assange would be able to invoke the First Amendment of the Constitution, which protects freedom of speech, and that he would be treated the same as any other US citizen.

The court also asked for guarantees that the death penalty would not be imposed. 

Stella Assange said she thought it was most likely that a decision would be made on Monday either to refuse permission for an appeal to be heard, or to grant permission and fix a date for it to be heard.

A third possibility, she said, was that the judges could decide to turn Monday's hearing into an appeal and even refuse the extradition request and free Assange.

"I think and I feel that anything is possible at this stage, that Julian could be extradited or he could be released," she said.

The WikiLeaks founder is expected to attend the hearing, having missed previous ones because of ill health, but remains frail, his wife said. 

"He is surviving and he is fighting to survive, and it is a daily struggle. Every assessment has said that there is a very serious risk of suicide," she said.

Two members of the press freedom organisation Reporters Without Borders (RSF) and Amnesty International's legal adviser, Simon Crowther, will be in court as observers.

RSF's UK campaigns director, Rebecca Vincent, said what was at stake was the freedom of the press to publish stories in the public interest based on leaked information. 

"What is at stake here is normal journalistic practice. If Julian Assange is taken to the US, if he is prosecuted under the Espionage Act, it sets a precedent for the same kind of case to be brought against any publisher, any journalist, any source, any organisation that works with leaked classified information," she said.

The US wants to put Assange on trial over the publication from 2010 of more than 700,000 classified US military and diplomatic documents, mainly relating to the wars in Iraq and Afghanistan.

Among the documents was a video showing a US helicopter gunship firing on civilians in July 2007, killing more than a dozen people, including two Reuters news staff.

Under the US Espionage Act of 1917, which the US authorities have invoked, Assange could face a prison sentence of up to 175 years.

On Tuesday, the Council of Europe's Parliamentary Assembly's rapporteur on the case, Sunna Ævarsdóttir, visited Assange in prison and again expressed concern about the conditions of his six-year detention in the high-security Belmarsh prison. 

"Regardless of whether or not he is extradited, his indictment and prolonged detention already have a chilling effect on other whistleblowers and journalists from exposing wrongdoings by governments or powerful private actors," she said in a statement.

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