LONDON, SEPT. 14 -- Britain today became the first European country to commit substantial ground forces to the Persian Gulf, ordering an armored brigade of more than 6,000 troops and 120 tanks to Saudi Arabia in response to a U.S. plea for more military support from Western nations.

While it pales beside the massive U.S. military deployment in the region, the British commitment was considered a major step here, one that was hotly debated for several days by Britain's defense chiefs and by a special cabinet defense committee.

Some politicians reportedly would have preferred to send fewer troops, but they were overruled by the generals, who warned that dividing the brigade in half would have greatly lessened its effectiveness.

Prime Minister Margaret Thatcher also is said to have argued that a smaller force might have sent the wrong signal both to Washington, which welcomed the British move, and to Iraqi President Saddam Hussein. Thatcher was the only foreign leader singled out for praise as a dependable ally by President Bush in his speech this week to Congress.

No other European country has committed a large number of ground forces to the gulf, and U.S. Secretary of State James A. Baker III got a cold response earlier this week when he pleaded with NATO members in Brussels to send military and economic support to the region. Britain, which has more nationals in Kuwait and Iraq than any other Western state, has prided itself on being swift and steadfast in its support for Washington, and Thatcher has chided other European nations for their reluctance.

In announcing the move, Defense Secretary Tom King said the commitment would double the cost for British forces in the gulf to nearly $4 million per day, plus some $190 million in "start-up" expenditures. That was further bad economic news on a day when the government announced that inflation last month reached an annual rate of 10.6 percent -- the first time the rate had reached double digits since 1982 and another sign that Britain is slipping into a recession.

Opposition politicians, who are reluctant to be seen splitting the popular consensus on the gulf crisis, for the most part endorsed the troop deployment. "The political point is not to massage American public opinion but to reaffirm our resolve to see that the United Nations resolutions are carried out and the legitimate government of Kuwait is restored," said Menzies Campbell, defense spokesman for the minority Liberal Democrats.

But Tony Benn, a left-wing Labor Party member who has led the small but vocal opposition here to the gulf buildup, said the deployment increased Britain's chances of being dragged into a war.

"It strengthens the opinion that President Bush intends to have a war against Iraq and wants Britain politically involved," said Benn.

King told a press conference that Britain would send the Seventh Armored Brigade, which is known as the "Desert Rats" for its World War II exploits against German forces in North Africa. It contains two armored regiments with 120 Challenger tanks, an infantry battalion equipped with armored cars, an armored reconnaissance squadron and an artillery regiment. It also has an air defense battery with helicopters and anti-tank and anti-aircraft missiles.

The brigade will be dispatched from bases in West Germany and could take three weeks to arrive in the gulf, King said. He added that Britain also would send a squadron of Tornado GR1 ground attack aircraft and some Tornado F3 air defense fighters to supplement aircraft already deployed in the region.

The purpose of the new deployments, said King, was to protect Saudi Arabia and the gulf states and "to ensure that Saddam Hussein understands that while we seek the implementation of the United Nations resolutions by peaceful means, other options remain available and, one way or another, he will lose."

Opposition politicians made clear that their support for the government's handling of the gulf crisis would not spill over into other areas, especially the economy.