LONDON, AUG. 20 -- Throughout the intensifying Persian Gulf crisis, one senior Western leader known for her outspokenness on the world stage has been conspicuous by her silence -- Prime Minister Margaret Thatcher.

The entire British government, in fact, has adopted a generally low-key approach to the gulf defense effort, which so far has enjoyed the support of ruling and opposition party members alike.

But this is not because the British have little at stake in the region; in fact, 4,000 British nationals are being detained by Iraqi authorities in Kuwait and Iraq -- more than any other Western nation -- and Britain has committed more forces to the Persian Gulf than any nation besides the United States.

London has maintained its subdued approach in part because of Thatcher's strong belief that this is George Bush's show and that her role as faithful ally is to render full support and stay out of the way, according to a senior Thatcher adviser.

Analysts said it also reflects a recognition here that there is a limit to what Britain can do to influence events, especially when it comes to the emotionally charged issue of the detained foreign nationals.

Thatcher was preparing to meet Bush in Aspen, Colo., when Iraqi forces invaded Kuwait on Aug. 2, and she wasted no time in advising the president to commit U.S. troops to the region to help prevent further Iraqi aggression. Thatcher sent British forces to the gulf, as well.

After holding a brief press conference in Washington to express strong support for Bush's effort to isolate Iraq, Thatcher went away on vacation, and for two full weeks there has been no public word from her on Britain's worst foreign-policy crisis since the Falklands War eight years ago.

As the crisis over detained foreign nationals in Iraq and Kuwait mounted over the weekend, virtually no one in authority here spoke at all. Senior British officials were not available for comment, and relevant government agencies were manned by tight-lipped duty officers who doled out few facts and no analysis. Officials also took care not to call any of the detained Britons "hostages."

The government's fears were underscored today when the Foreign Office announced that Iraqi occupation troops had moved 82 Britons from the Regency Palace Hotel in Kuwait on Sunday, bringing to 123 the number of British citizens seized since Saturday. Foreign Secretary Douglas Hurd branded the move "illegal and repulsive," and said "a number" of Britons had taken refuge at the British Embassy in Baghdad.

Pressed in a British Broadcasting Corp. interview about what Britain was doing to free its citizens beyond diplomatic discussion, a clearly frustrated Hurd disclosed some of the constraints that officials here are operating under.

"What alternative do you suggest?" asked Hurd, who has been Britain's principal spokesman during the crisis. "It is really not sensible to think in terms of measures which would add to the danger of the people we are trying to protect.

"What the Iraqis are doing has mobilized against it a huge weight of opinion including, for example, the Russians, traditionally friends of Iraq. What we must try to do is keep that pressure up by every means that we can think of."

Asked about the chances of a military rescue of the detained foreigners, Hurd replied: "Just think it through. Think it through. How would you propose to carry that out in a way which gave any chance that the people you were trying to rescue would be alive at the end of the day?"

Thatcher returned to Downing Street Sunday night after 10 days in southwest England. She was briefed this morning by Hurd and Defense Secretary Tom King and spent 20 minutes on the phone with Bush. But today's only public remarks came from Hurd, a veteran diplomat, who told reporters that the crisis over the detained foreigners "is going to be a very difficult business and may go on for some time."

But after two weeks of near total support, domestic criticism of the government's low-key approach is slowly increasing. Several senior members of Thatcher's Conservative Party have demanded that she call Parliament into special session to approve British military involvement in what could likely become a shooting war. Others are grumbling that she has fallen victim to what one called "the Foreign Office mentality."

"The feeling of the bureaucrats is that we're not in the driver's seat, and it all may end up in disaster, so let's play it as long and as low as we can," said a senior Conservative member of Parliament who is a Thatcher supporter. "But if it comes down to military confrontation, Britain will want to look part of a multinational show, not dragged along at the end of the American pole.

"It's amazing," he added, "that so far there has been no clear statement of British objectives. No one has set down where we are and what is at risk."

Thatcher's government is clearly relishing the role of loyal U.S. ally -- and pointing out the sharp contrast between its own approach and that of other, more hesitant West European nations. In doing so, it is reasserting Thatcher's traditional view that Britain's values and fate are more closely linked to Washington than to Bonn or Paris.

"You make choices," said the Thatcher adviser. "Either you're with the only superpower in the world, or you're on the sidelines. Remember Germany? A few weeks ago that's all we were hearing about. Where's France? George Bush may have had a flirtation with the Krauts, but we suspect he can see where his real friends are now."

Thatcher has been able to stay silent on the crisis in part because opposition Labor Party leader Neil Kinnock has allowed her to. Kinnock returned from his own vacation in Italy over the weekend and signaled his agreement with her approach, contending anything more public might only play into the hands of Iraq by dramatizing the crisis and inflaming public emotions.

But the question of British hostages is changing the political calculation. When the Iraqi order for British and American nationals in Kuwait to report to local hotels first arrived at the Foreign Office Thursday, Hurd was on vacation in southern France and William Waldegrave, the junior minister in charge, gave an angry public response that raised the issue of internment.

It was a far stronger statement than anything issued from Washington, but it was accompanied by a tacit suggestion that British nationals comply with the order.

By Thursday night, Hurd was back, and the low-key approach returned as well. The suggestion to report to hotels was rescinded; Britons were to sit tight and exercise caution. When Iraq repeated the order Sunday, Waldegrave made no comment.