Gary McKinnon, accused of hacking into 53 US military and Nasa computers in 2001 and 2002, appeared at Bow Street Magistrates' Court in London.

The 39-year-old, of Wood Green, north London, will be back in court for an extradition hearing on 27 July.

His lawyer said he would contest extradition to the US "vigorously".

Mr McKinnon, an unemployed computer systems administrator, is known on the internet as "Solo"

He is accused of hacking into computer networks operated by Nasa, the US Army, US Navy, Department of Defence and the US Air Force.

One of the networks belonged to the Pentagon.

The US estimates the costs of tracking and correcting the problems he allegedly caused were around $1m (£570,000).

If he is extradited and found guilty, Mr McKinnon faces a maximum penalty of five years in prison and a £157,000 fine.

The Briton was indicted in 2002 by a federal grand jury on eight counts of computer-related crimes in 14 different states.

It claimed that he hacked into an army computer at Fort Myer, Virginia, obtained administrator privileges and transmitted codes, information and commands.

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Unauthorised access

He is accused of then deleting around 1,300 user accounts.

The indictment alleged Mr McKinnon also deleted "critical system files" on the computer, copied a file containing usernames and encrypted passwords for the computer and installed tools to gain unauthorised access to other computers.

A loss of over $5,000 (£2,725) to the Army stemmed from the alleged damage, according to the indictment.

At the time of the indictment, Paul McNulty, the US Attorney for the Eastern District of Virginia, said: "Mr McKinnon is charged with the biggest military computer hack of all time."