Up to 800 British military personnel will take part in a major US-led war exercise co-ordinated from Qatar, UK military sources have confirmed.

The exercise, which is due to take place sometime next week, is seen as a build-up to any potential military intervention in Iraq.

The 400 British military staff already in Qatar will be joined by a further 400 British staff taking part from bases in the UK, the US and elsewhere in the Middle East.

Codenamed Internal Look, the wargame will test the effectiveness of the US central command centre (Centcom), which has been set up at the As-Sayliyah army base near Doha.

The BBC's defence correspondent Paul Adams says the size of the UK's participation suggests that Britain is ready to send a substantial number of troops to the Gulf if a political decision is taken to go to war.

'Command and control' centre

British staff will join up to 1,000 US military personnel including top war planners being deployed to Qatar in advance of the exercise.

The command base, led by General Tommy Franks, will act as a portable HQ and communications system which is set to lay important groundwork for a potential Iraq campaign.

Saudi Arabia has blown hot and cold over the presence of US troops

Commanders of the Navy, Army and Marine Corps units in the region will also take part.

US Defense Secretary Donald Rumsfeld is to visit Qatar in mid-December on a trip coinciding with the wargames, a US embassy spokesperson said Tuesday.

'Good contingency'

UK military sources said "common sense" dictates that although Internal Look has been planned for some time, the exercise is "a very good contingency measure" for any future campaign.

Pentagon officials have already privately said that 600 US military personnel in Qatar for the exercise may stay on once it is over.

More than 4,000 US military personnel are already in the Gulf state.