Britain ordered a task force of ships and 3,000 Royal Marines to head toward the Persian Gulf and mobilized 1,500 reserve soldiers Tuesday for possible war on Iraq, joining the United States in stepping up military pressure on Saddam Hussein.

France, which has resisted Washington's tough line on Iraq, gave its clearest sign yet it would participate in military action if Baghdad does not eliminate weapons programs. President Jacques Chirac told French troops to be prepared for deployment.

British Defense Secretary Geoff Hoon announced the mobilization of the reserves during a speech to the House of Commons in London. The initial call-up was for 1,500 soldiers, with more to come, he said.

"Whilst we want Saddam Hussein to disarm voluntarily, it is evident that we will not achieve this unless we continue to present him with a clear and credible threat of force," Hoon told lawmakers.

Hoon also said a "significant" force of Royal Navy vessels and Royal Marines would be sent to the Mediterranean to train for possible action in the Gulf. A Ministry of Defense official said about 3,000 Marines would be aboard the ships, which include an aircraft carrier and three destroyers.

In Paris, Chirac said French forces probably will continue to be needed in certain "operational theaters," a reference to Ivory Coast where France has more than 2,000 troops. However, he added, "other [theaters] could open up," a reference to Iraq.

In Washington, Defense Secretary Donald H. Rumsfeld said Tuesday that war with Iraq is "not inevitable," but he said Iraq is not complying with U.N. demands that it rid itself of chemical, biological and nuclear weapons programs.

Tens of thousands of U.S. combat troops are heading for the Gulf in a mobilization that will double the contingent to more than 100,000 by the end of January and to 200,000 by the end of February. The eventual fighting force could swell to about half the 550,000 U.S. troops amassed in the 1991 Gulf War.

Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said the military was deploying "to provide the president as much flexibility as possible," should he decide to wage war.

The United States has threatened to use force to disarm Iraq if it does not give up weapons of mass destruction as required by Security Council resolutions.

Iraq maintains it has no banned weapons and so far has cooperated with U.N. weapons inspectors, who resumed their work two months ago -- backed by a tougher resolution from the Security Council -- after a four-year absence.

On Tuesday, inspectors used helicopters for the first time in their search for banned weapons, with three choppers lifting off from a Baghdad military base to conduct an aerial survey. The aircraft will make it easier for inspectors to swoop down on potential weapons sites.

Inspectors on the ground visited at least six sites, including a factory producing Iraq's al-Samood missiles, a Baghdad cancer research center and a cement factory. The inspectors apparently were interested in the cancer center's radiation techniques, and cement companies can materials that may be employed in weapons manufacture.

Britain has been Washington's strongest backer toward Iraq, while France has been more reluctant, insisting the United States cannot launch military action without U.N. support.

On Tuesday, however, Chirac said in a New Year's message to the armed forces that they should be prepared for deployment.

British Prime Minister Tony Blair told a conference of 150 British ambassadors on Tuesday, "If the will of the U.N. is breached, then the will should be enforced."

Blair's government has said it would prefer the Security Council pass a second resolution supporting force before taking military action, but that it could join the United States in war without one.

Hoon said a force of three destroyers, a helicopter carrier and several landing and support ships would head to the Mediterranean to train for possible deployment in the Gulf. The ships will carry troops from 40 Commando Royal Marines and 42 Commando Royal Marines, he said.

The government announced Monday that another task force of six vessels -- including an aircraft carrier, a submarine, a frigate and a destroyer -- would stop in the Gulf en route to a training exercise in Southeast Asia.

Both groups of ships were to sail from Britain on Saturday. Hoon said the deployments were intended "to keep open a range of military options" and that more would likely follow in the next few weeks.

Apart from Britain, few of the United States' 30 allies in the 1991 Gulf War have offered much in the way of support this time.

The Mideast countries that sided with Washington in 1991 -- Saudi Arabia, Qatar, Bahrain, Oman, the United Arab Emirates, Egypt and Syria -- all say they won't act without U.N. approval, though Pentagon officials say Saudi Arabia has privately assured them U.S. troops could use bases there for air support missions.

Qatar has allowed the United States to beef up a potential command-and-control base, Camp As Sayliyah, for a possible war on Iraq. The United States has bases in nearby Bahrain, Kuwait and Saudi Arabia, which it is expected to use to support any war effort.

Turkey, which served as a staging point for air attacks against Iraq during the 1991 war, has not yet committed to allowing the use of its territory or air bases -- crucial to any U.S. war effort. However, Turkey has been moving soldiers into northern Iraq, doubling its presence in the area to some 12,000 troops, a senior intelligence source said Tuesday in Ankara.

European countries have been lukewarm. German Chancellor Gerhard Schroeder has said repeatedly that his country will not provide combat troops. However, he has agreed to let the U.S. military overfly Germany and use its bases on German soil to support an attack on Iraq.

The Australian government has said it would not rule out sending troops to Iraq in the event of a U.S.-led war, even without U.N. backing, and has ordered its armed forces to begin making preparations.