SLAMABAD, Pakistan, Sept. 19 — Pakistan's military ruler, Gen. Pervez Musharraf, went on nationwide television tonight to offer a tense, sometimes emotional defense of his decision to join the United States in the hunt for Osama bin Laden. General Musharraf said the situation presented this volatile Muslim nation of 140 million people with its gravest crisis in the 30 years since it lost its last major war, with India.

"Trust me," he said in a 20-minute speech as he confirmed that the United States had asked to use Pakistan air space and sought its intelligence about Mr. bin Laden and its logistical support for a possible military thrust into Afghanistan.

He made no mention of United States ground troops or special forces' using air bases in Pakistan, a possibility widely discussed here as close to 100 American bombers, fighters and other war planes moved toward the Middle East with their final destination unknown.

"I have fought in two wars, and by the grace of God, I have never shown any timidity," the general said, answering opponents who have accused him of weakness for bowing to intense American pressure for Pakistan to be used in any American military operation.

General Musharraf spoke as the crisis started by the attacks on New York and Washington appeared to move closer to a showdown.

In Kabul, the capital of Afghanistan, a meeting of 700 Muslim clerics from the Taliban movement that governs most of the country seemed near a final decision not to hand over Mr. bin Laden. The clerics are deciding under American military threats, although there were signs that the decision could be delayed until Friday or later.

General Musharraf said categorically that the Taliban had rejected a handover. But there were signs in Kabul of continuing uncertainty and splits in the Taliban movement.

The speech had nervous Pakistanis stopping in bazaars, airports and hotel lobbies to crowd around television sets, eager to hear the general explain why he had promised President Bush "full support" for an American military operation.

That support has already carried a high political price. Islamic militant groups linked to Mr. bin Laden and some political parties have promised to do everything possible to disrupt an American military venture involving Pakistan, beginning with a call for a general strike on Friday.

Militants have held noisy protests in dozens of cities and towns, burning Mr. Bush in effigy and promising a "holy war" against any American troops setting foot here. The possibility that American pressure could destabilize Pakistan or even throw the country into chaos appeared real.

The speech appeared intended to buy time by suggesting that American action was not imminent and to rally support by stating that if Pakistan did not back the United States, its rival, India, would exploit the situation. Speaking of India, a country with which Pakistan has a deep conflict over Kashmir, General Musharraf said, "They want to enter into any alliance with the United States and get Pakistan declared a terrorist state."

Pakistan and Afghanistan share a 1,500-mile border of deserts and mountains. Some of Pakistan's major air bases lie 10 or 15 minutes' flying time from possible targets around major Afghan cities.

Even as the Pentagon moved additional combat aircraft and ships into the region, it was unclear how far off any American assault might be.

General Musharraf, evidently marked out as a major partner in any strike, said that based on what Pakistan knew, "the American plans are not ready" and had not reached the point where details of Pakistan's involvement have been discussed.

The general, who took power in a coup less than two years ago, said that for him "Pakistan comes first, and everything else second." It was that approach, he added, that had led him to choose cooperation with the Americans, with its risks of domestic upheaval, over defiance that might have made a pariah of Pakistan.

Pakistan has sought to have sanctions against it erased, and the United States plans to make its case for lifting sanctions this week, congressional officials in Washington said.

General Musharraf's assertion that his air force had been put on its highest state of alert to guard against a possible Indian attack on nuclear sites appeared to alarm Mr. Bush. In two hours, Mr. Bush told reporters in the Oval Office that in the diplomacy surrounding the terrorist attacks "we will work with Pakistan and India to make sure that that part of the world is as safe as we can possibly make it."

In Kabul, the Taliban gathered its top clerics in a shura, or grand council, in a meeting hall in the old royal palace that has been used at critical junctures in Afghanistan history — by kings, Communist rulers and, now, clerics — to discuss and ratify important decisions. Television pictures showed dozens of the heavily bearded clerics in flowing white robes and turbans walking through the grassy courtyard. They began deliberating by reading a defiant speech by the supreme leader of the Taliban, Mullah Mohammed Omar, who has led the campaign to impose its medieval version of Islamic rule.

General Musharraf said his military delegation to Afghanistan returned from talks with Mullah Omar and others on Tuesday night with a rejection of the American demand that they surrender Mr. bin Laden to face trial for terror acts and interrogation as Washington's "prime suspect" in the attacks last week.

Mullah Omar, in the text read in Kabul, continued to waver on the issue. The speech mixed defiant statements about never handing over Mr. bin Laden with suggestions that the Taliban might agree to a deal under certain conditions.

He was willing to talk to the United States about Mr. bin Laden, he said, but not under ultimatums and not until the Taliban had been shown evidence of Mr. bin Laden's involvement in the attacks.

"Our Islamic state is the true Islamic system in the world, and for this reason the enemies of our country look at us as a thorn their eye and seek different excuses to finish it off," Mullah Omar said, according to Reuters. "Osama bin Laden is one of these."

Still, the Taliban leader played for time. "We appeal to the American government to exercise complete patience," he said, "and we want America to gather complete information and find the real culprits."

Gen. Musharraf, too, appeared keen to delay. Since his quick commitment to cooperate with the United States, leaders of nations that have strong influence with Pakistan, including Egypt and China, have warned of the risks in the "war" Mr. Bush has pledged.