The likelihood of British hacker Gary McKinnon's extradition to the United States to face hacking charges moved a step closer, after British authorities said they won't prosecute him in the United Kingdom.

McKinnon, of London, has said he would plead guilty to an offense under the UK's Computer Misuse Act if he could stay in the country rather than face trial in the US District Court for the Eastern District of Virginia, where he was indicted in November 2002.

McKinnon faces charges of illegally accessing and damaging US government computers. The US government alleges his exploits cost at least $700,000 (£490,500) and caused the shutdown of critical military networks shortly after the 11 September, 2001, terrorist attacks. McKinnon could face a sentence of 60 years or more.

A Crown Prosecution Service spokesman said Thursday that the US has always wanted to maintain jurisdiction. UK prosecutors agreed in 2002 to cede jurisdiction since the harm occurred inside the United States, most witnesses are there, and the bulk of evidence was in the US, among other reasons, the spokesman said.

McKinnon's law firm, Kaim Todner, said that prosecutors made the decision not to prosecute, leaving him subject to extradition, before even asking the US for evidence.

But McKinnon is still fighting his extradition on another issue. He is appealing an extradition order approved by the UK secretary of state on the basis of his recent diagnosis of Asperger Syndrome, a neurological disorder characterised by obsessive behaviour and deficiencies in social interaction.

He's asked for a judicial review of the extradition order by the High Court, said his attorney Karen Todner. No date for the review has been scheduled.

McKinnon has publicly admitted to breaking into the US military systems, saying he was looking for evidence of UFOs. He used a program called "RemotelyAnywhere" to control US military computers, many of which only used default passwords, which made them easy to access.

He timed his hacking during the US night-time, but on one occasion miscalculated the time difference. Someone noticed a cursor moving on its own on a computer and severed the Internet connection. It prompted an investigation, and UK police eventually arrested him.