SLAMABAD, Pakistan, Sept. 15 — Pakistan today pledged its "full support" in the hunt for those responsible for the terrorist attacks on the World Trade Center and the Pentagon, but carefully avoided any specific commitment to provide the United States with military assistance in an operation against terrorist bases in neighboring Afghanistan.

Pakistan's military-led government also said it would "continue to act in conformity with its support of the state of Afghanistan," an expression of backing for Afghanistan's militant Islamic Taliban government that suggested how torn Pakistan is between the United States' demands and the sympathies of many of its people.

By avoiding any specific promises of military support for the United States and taking a nonconfrontational line with the Taliban, the Pakistani government was clearly seeking to cleave to some tenuous middle ground.

President Pervez Musharraf fears a violent backlash in Pakistan if he follows Saudi Arabia's example after the Iraqi invasion of Kuwait in 1990 and allows American troops free rein on his territory, officials said.

He also faces the prospect of a direct confrontation with the Taliban, who harbor the terrorist suspect Osama bin Laden and who today threatened "a massive attack" by its Islamic warriors if Pakistan offers the United States any assistance.

In response to American requests to use Pakistan as a launching pad for a military attack on Mr. bin Laden and his followers, an official statement today said Pakistan would comply with a United Nations Security Council resolution passed within 36 hours of the attacks in New York and Washington that called on all nations to cooperate in tracking down those responsible. But Pakistan declined to go beyond that formalistic undertaking.

The Bush administration is pushing for more unequivocal assistance. The Pentagon views Pakistan's cooperation in a military campaign as crucial because of the absence of any other American bases on Afghanistan's borders and because access to the landlocked, mountainous country from anywhere else would be arduous or impossible.

Although General Musharraf theoretically has unlimited powers as a military ruler, he is constrained in practice by strong centers of support for Islamic militancy in the Pakistani officer corps and in the hard- line Islamic groups that have proliferated across the country in the last decade.

Whichever way he moves, General Musharraf, who took power in a coup almost two years ago, could hardly be assured of the undivided support of this deeply unstable nation.

Pakistan, a poor country of 140 million people awash in debt and Kalashnikovs — and now nuclear armed — has a growing number of destitute Muslims who have embraced the radical Islam of the Taliban as their only source of hope. Some of them also sympathize with the violent anti-American campaign of Mr. bin Laden.

Pakistan's backing for the Taliban, which continued despite its harboring Mr. bin Laden after previous terror attacks against American targets, has been crucial to the survival of the government in Kabul.

While educated Pakistanis with Western sympathies embrace the United States, many people here recall and resent the fact that it was the United States that first backed and financed the Islamic radicals in the 1980's, using them as a vehicle to fight Soviet forces in Afghanistan. The United States' No. 1 enemy, they point out, is in a sense one of the United States' own creation.

At a news conference today, Foreign Minister Abdul Sattar refused to answer a barrage of questions about Pakistan's willingness to agree to American proposals that emerged from days of intensive discussion between the two nations, calling them "details" that remained to be settled.

The statement distributed at the news conference said General Musharraf had met with top cabinet and security officials today for fours hours of "incisive discussion," after a similarly long meeting on Friday with the country's top generals.

The statement said today's meeting had "reached consensus on the policy of full support to the world community in combating terrorism." It added, "Consistent with Pakistan's policy of support for the decisions of the Security Council, the government will discharge its responsibilities under international law."

The foreign minister said it was not necessary for Pakistan to respond in detail to the American demands, since no plans he knew of had been set for a military attack.

But his comments, including an insistence that Pakistan did not intend to wage war against its neighbor or commit troops outside its own borders, implied that General Musharraf intended to strike a careful compromise, granting Washington at least some use of Pakistan's airspace and military bases, while limiting its cooperation so as not to be seen as a full-fledged partner in a military campaign.

The Bush administration has told the Islamabad government, under the implied threat of economic and other penalties, that it wants the use of Pakistani airspace and military airfields, as well as full access to the unique store of intelligence about Mr. bin Laden's operations in Afghanistan that has been gathered by Pakistan's military intelligence agency.

Washington has also demanded a cutoff of fuel supplies, an end to the use of Pakistani banks as conduits for clandestine money movements by terrorists and the elimination of truck convoys that provide much of the food and other supplies to Afghanistan's civilian population.

But Foreign Minister Sattar said today that Pakistan would continue "to exchange views with the government of Afghanistan in a spirit of friendship and fraternity."

He dwelled at length on Pakistan's warm relations with the "Islamic Emirate of Afghanistan," the formal name adopted by the Taliban.

The foreign minister chose that friendly tone despite a warning from the Taliban, issued through its embassy in Islamabad, that "the possibility of a massive attack by our holy warriors cannot be ruled out if any neighboring country offers its ground or air bases to U.S. forces."

The Pakistani ambivalence posed a clear problem to the Bush administration: how to mount the large-scale military operation that many believe would be needed to hunt down an elusive enemy — Mr. bin Laden and his followers constantly move around Afghanistan's deserts and mountains — without a secure land base in the region.

One possibility seemed to be that American troops and supplies would be staged through Pakistani airspace and airfields on their way to building bases inside Afghanistan.

Another deep problem is this: Might winning the cooperation of Pakistan lead to the destabilization of the country, which detonated a nuclear bomb in 1998, and its possible takeover by the very radicals the United States is trying to suppress or eliminate?

The specter of regional instability was underscored today when Iran, which already harbors more than a million Afghans who have fled almost two decades of war, said it was bolstering its military and police forces along its long frontier with Afghanistan and closing the border to head off a new influx of refugees. The announcement came even as many residents of Kabul, the Afghan capital, began packing up in anticipation of an American strike.

Although Foreign Minister Sattar refused to go into details of what, if anything, had been agreed with the United States, he appeared to be setting limits to Pakistan's role. At one point, he entered what sounded like a dissent to American references to "war."

"I have not said at any time that Pakistan is going to be participating in a war against any country," he said. At another point, he said Pakistan's role would be strictly domestic. "Pakistan does not expect in any way to participate in any military operations beyond our borders," he said.

If Pakistan seems ready to be obdurate about the Taliban, it could be because it believes that the United States, on this score, is hardly in a position to condemn Pakistan.

At a crucial moment in 1996, days after the Taliban overran Kabul in a display of brutality, the Clinton administration decided to seek friendly ties with the Islamic movement. The plan was abandoned after the Taliban began oppressing women, but American diplomats continued to say until the bin Laden terror attacks became a focus of American policy that the Taliban might be the best government Afghanistan could hope for after a generation of conflict.