The Western allies are gearing up their troops for possible deployment to the Gulf in the event of a war with Iraq.

The UK said it was calling up 1,500 reservists, with more to follow if necessary, and bolstering naval forces already earmarked for the Gulf.

The threat of force must remain Geoff Hoon, UK defence secretary

In France, President Jacques Chirac said soldiers needed to be prepared in case new areas of engagement opened up - his clearest reference yet to the prospect of French involvement in any military action in Iraq.

And the United States Central Command has said it is dispatching battle staff to a new forward headquarters in Qatar, in the latest sign that Washington's build-up is gathering pace.

Meanwhile US leaders have been reiterating their determination to use force if necessary while saying there were alternatives.

Their remarks came as United Nations weapons inspectors continued to search Iraq for the weapons of mass destruction.

War 'not inevitable'

"Saddam Hussein must disarm himself of all weapons of mass destruction and prove that he has done so," said President Bush on Tuesday.

The UK has ordered a task force to the Gulf

"Should he choose the other course, in the name of peace, the United States will lead a coalition of the willing to disarm the Iraqi regime of weapons of mass destruction and free the Iraqi people."

Defence Secretary Donald Rumsfeld said that war was possible but not inevitable, adding that he hoped Saddam Hussein would leave the country.

"I still hope that he'll leave," he said. "And I hope that the country will be disarmed. And I hope that force will not have to be used. But in the meantime we'll keep flowing forces."

Threat of force

The UK Defence Secretary Geoff Hoon told parliament on Tuesday the reservists were being mobilised "for possible actions against Iraq".

Chirac: Readying French public opinion for possible military action

He also said a "significant" force of vessels would be sent to the Mediterranean in preparation for possible action in the Gulf, in addition to a task force due to set sail for the region on Saturday.

The defence secretary said no decision had been taken to commit these forces to action, but "as long as [Iraqi President] Saddam's compliance with United Nations Resolution 1441 is in doubt, as it is at present, the threat of force must remain".

So far, few of America's other allies have made any definite practical commitments to joining possible operations against Iraq.

Chirac warning

Alluding to Iraq, the French president, meanwhile, warned his troops that other theatres of engagement could open up, in addition to areas where French soldiers are currently engaged.

"Particularly, we have to be attentive to the way in which United Nations Security Council resolution 1441 is applied by Iraq," he said.

The BBC's Paris correspondent, Jon Sopel, says Mr Chirac is slowly trying to massage public opinion, readying it in case military action does take place and French soldiers are called to serve alongside American troops.

France has long opposed the prospect of unilateral military action by America against Iraq, insisting any resort to force must be approved by the UN first.

US deployment

Thousands of American soldiers are being deployed to the region this week, joining the 50,000 already there.

The Comfort has 12 operating theatres

The White House has also ordered the aircraft carrier USS Abraham Lincoln to abandon its voyage home and return to Australia, fuelling speculation that plans are being made to use the vessel in a campaign.

The giant US Navy hospital ship, USS Comfort, also left her home port of Baltimore on Monday and is thought to be heading to Diego Garcia in the Indian Ocean.

At least 10,000 US reservists have been told to prepare for possible overseas deployment as early as this week to support the build-up.

The US Army has also started deploying more than 11,000 soldiers from the 3rd Infantry Division in Fort Benning and Fort Stewart in Georgia - specialists in desert warfare.

Correspondents say that many of these troops are veterans from Desert Storm, the US-led military operation to remove the Iraqi army from Kuwait over 10 years ago.