The UK's military options

HMS Illustrious is on its way to the Gulf Region

By BBC defence correspondent Jonathan Marcus

Britain has given the strongest backing yet to President George Bush out of all of Washington's European allies.

Preparations are currently under way for one of the largest ever British military exercises in the Gulf

Britain is also a key player in welding together a much broader coalition to back US military action but could British help include practical military assistance?

Much depends upon what the Americans decide to do but it is clear that there are a number of areas where Britain could perhaps help.

What is driving the speculation about a British military role is the fact that preparations are currently under way for one of the largest ever British military exercises in the Gulf.

Troop deployment

Up to 6,000 British troops are being deployed to Oman in an operation called "Saif Sareea Two" and involving ground, air and naval forces.

The bulk of the British troops comprise an armoured brigade with headquarters and supporting elements.

Will Britain have an active role in punitive attacks?

A strong naval force is also already on its way to the Gulf region - some 24 surface ships in all, together with two submarines.

Among the vessels are the aircraft carrier HMS Illustrious, with both Navy Sea Harriers and RAF Harrier GR7s on board, the helicopter carrier HMS Ocean and the assault ship HMS Fearless.

Royal Marines from 3 Commando Brigade will be staging landings on the Omani coast and over 30 combat aircraft are also due to take part in the exercise, which extends through to October.

The US military was hugely impressed by SAS operations during the Gulf War

The troops are arriving in Oman over the next few days and the naval element is currently in the Mediterranean.

According to the Ministry of Defence in London, everything is going as planned except that some key elements of the Joint Forces Headquarters that were intending to deploy to Oman are now staying in Britain.

Potent military force

All this represents a potent military force but it is far from clear how relevant it is to the sort of operation the Pentagon may have in mind.

One of the two submarines, HMS Trafalgar, is capable of firing land attack cruise missiles, and the carrier-borne aircraft could theoretically take part in any joint operation with US warplanes.

Blair faces a testing time over the extent of British involvement

But the Americans may want British assistance in another area.

The US military was hugely impressed by SAS operations behind Iraqi lines during the Gulf War.

Some in the SAS already have experience of operating in northern Pakistan.

While no defence sources venture any comment on special forces operations, this may be the critical area where British help and experience is most needed.