Briton Gary McKinnon leaves the High Court in central London in January 2009. McKinnon, accused of hacking into US military and NASA computers, faces extradition to the United States after the British government Thursday rejected last-ditch requests to block the move.

A Briton accused of hacking into US military and NASA computers faces extradition to the United States after the British government Thursday rejected last-ditch requests to block the move.

Home Secretary Alan Johnson said he concluded that sending Gary McKinnon to the United States would not breach his human rights, and has no general discretionary powers to stop the extradition.

"If Mr McKinnon's human rights would be breached, I must stop the extradition. If they would not be breached, the extradition must go ahead," Johnson said in a statement.

"As the courts have affirmed, I have no general discretion," he said.

McKinnon, who suffers from a form of autism, could spend life in prison if convicted by a US court of gaining access to 97 computers in 2001 and 2002 in the aftermath of the September 11, 2001 attacks.

McKinnon says he was only looking for evidence of unidentified flying objects (UFOs) when he hacked into the US Navy and space agency computers.

Throughout the long-running case, McKinnon's lawyers have argued against extradited in part because he suffers from Asperger's Syndrome, and could commit suicide or suffer psychosis if it went ahead.

McKinnon's mother slammed the minister's decision as "barbaric".

Janis Sharp warned that the 43-year-old was terrified of extradition and the case has taken its toll on his mental health.

"To force a peaceful, vulnerable, misguided UFO fanatic like Gary thousands of miles away from his much-needed support network is barbaric," Sharp said.

"This is a cruel and miserable decision," she said, adding that the , should "hang their heads in shame."

"If the severity of Gary's medical condition isn't sufficient to prevent his extradition, I can't imagine what is. God help others facing a similar fate."

His cause has drawn high-profile support, including from Trudie Styler, wife of rock star Sting, who urged Britons to write to the Home Secretary.

Last month, the High Court in London refused McKinnon leave to appeal to Britain's new Supreme Court against his extradition.

The Home Office agreed to study new medical evidence about McKinnon before deciding on his extradition.

But Johnson has since told McKinnon's family that he could not block the move on medical grounds.

He said however he had received guarantees from US authorities that McKinnon's medical needs would be met once extradited, and, if convicted, he would not serve any time in a "supermax" prison.

"Due to legitimate concerns over Mr McKinnon's health, we have sought and received assurances from the United States authorities that his needs will be met," Johnson said.

"Finally, should Mr McKinnon be extradited, charged and convicted in the US and seek repatriation to the UK to serve a custodial sentence, the government will, of course, progress his application at the very earliest opportunity."

McKinnon's solicitor said she would now seek a judicial review of Johnson's decision, and lodge an application before the High Court within seven days.

"We are certainly coming to the end of the road, but we are just hoping that at some point, someone sees sense and steps in," Karen Todner told the BBC.

"In some ways it's like dealing with a death row case, we genuinely believe Gary's life is at stake here."

His lawyers say he could easily be prosecuted in Britain, where he would face a less severe sentence. But the Crown Prosecution Service ruled in February that the case was best brought in the .

(c) 2009 AFP