Britain said on Tuesday that Gary McKinnon, an Asperger's sufferer who hacked into US military computers, will not be extradited to the United States, ending his 10-year legal battle.

Interior minister Theresa May said extradition would breach 46-year-old McKinnon's human rights as his psychiatrists believed there was a high risk that he would attempt suicide were he sent to the United States.

"Mr McKinnon is accused of serious crimes, but there is also no doubt that he is seriously ill," May, the Home Secretary, told parliament.

"I have concluded that Mr McKinnon's extradition would give rise to such a high risk of him ending his life that a decision to extradite would be incompatible with Mr McKinnon's human rights.

"I have therefore withdrawn the extradition order against Mr McKinnon."

The US said it was considering its options.

"The United States is disappointed by the decision to deny Gary McKinnon's extradition to face long overdue justice in the United States. We are examining the details of the decision," a State Department spokeswoman told reporters.

The spokeswoman, Victoria Nuland, insisted the 10-year legal battle had not undermined the close ties between London and Washington. "I think you know we have an incredible alliance and that will obviously continue," she said.

British prosecutors will now decide whether the hacker should face trial in Britain.

McKinnon's mother Janis Sharp -- who has campaigned vigorously for her son -- thanked May for having "the guts" to block the extradition and said her son was "incredibly emotional" at the decision.

He was arrested in London in 2002 for hacking into dozens of Pentagon and NASA computers, leaving 300 machines at a naval air station immobilised just after the September 11, 2001 attacks.

McKinnon has never denied the hacking, claiming he was looking for classified US documents on UFOs.

He could have faced up to 60 years in a US jail for the breaches, which the United States says caused $800,000 (615,000 euros) worth of damage.

The hacker, who has become a symbol of the campaign to revamp Britain's extradition deal with the United States, lost appeals in Britain's House of Lords and the European Court of Human Rights during his decade-long fight.

McKinnon was diagnosed with Asperger's, a form of autism, in 2007, after an expert on the condition watched him in a television interview and contacted the hacker's lawyer.

In an emotional press conference in London, his mother said she was "overwhelmed".

Fighting back tears, she said: "I'm incredibly happy. I want to say thank you to Theresa May, because it was an incredibly brave decision -- to stand up to another nation as strong and powerful as America is rare."

She said her son had not been able to speak when he heard about the decision.

It had been "horrendous" watching him mentally deteriorate over the last decade as the extradition process hung over him, she said.

"He felt he was dead," Sharp told journalists. "He would just sit in the dark all the time... we saw him shut down."

McKinnon's lawyer Karen Todner said it was "a great day for British justice".

"I have represented Gary for over 10 years," she told journalists. "It has been a rollercoaster and a hard fight, but worth it in the end."

She urged British prosecutors not to pursue a case against McKinnon, saying he had suffered enough over the last decade.

"There is very clear medical evidence that Gary is very depressed and possibly unfit to plead," she added.