ASHINGTON, Sept. 28 ・President Bush said today that the United States was "in hot pursuit" of both Osama bin Laden and the Taliban forces harboring him in Afghanistan.

Senior military officials insisted that there were no American military forces currently on the ground in Afghanistan. That, however, did not preclude the possibility that they had already gone in and come out.

Those and other officials would not discuss whether intelligence operatives had been in Afghanistan recently on reconnaissance or other missions, but one Pakistani intelligence official said allied special operations forces had been there. He declined to elaborate, but other officials suggested British Strategic Air Service units may have been in the country.

Mr. Bush said that, while he expected that "the American people won't be able to see what we're doing," they should "make no mistake about it, we're in hot pursuit." That choice of words may have been intended to deflect criticism from conservatives in Congress that his administration is moving too slowly to retaliate for the terrorist attacks.

Or it may have signaled real progress on the military and intelligence fronts about which the administration would have no interest in giving details that might prejudice continuing operations.

During an appearance in the Oval Office with King Abdullah of Jordan, the president also said that the coming campaign against those believed responsible for the Sept. 11 terrorist attacks would be a "guerrilla war."

Mr. Bush's statement today came as the White House, for the first time since the military planning began, gave a specific description of the administration's political goals in Afghanistan, and left little doubt that one objective is the forcible removal of the radical Islamic Taliban government.

"The Taliban do not represent the Afghan people, who never elected or chose the Taliban faction," said a document prepared by officials of the National Security Council and the State Department.

"We do not want to choose who rules Afghanistan," the document continued, "but we will assist those who seek a peaceful, economically developing Afghanistan, free of terrorism."

The days when military doctrine centered on the use of overwhelming force to crush a clear enemy appear to be over.

The president's comments today emphasized the role that special operations forces, rather than conventional military units, are expected to play in the first American military actions to punish Mr. bin Laden and his Al Qaeda network.

One defense official said that American reconnaissance forces have set up operations in neighboring Uzbekistan.

This week the United States and Pakistan established a joint military intelligence group to deal with what American officials say have been the frustrations of poor intelligence reports emanating from inside Afghanistan.

In his comments today, Mr. Bush made it clear once again that he did not intend to occupy Afghanistan, and suggested he had studied the unhappy history of countries that have tried to tame the remote and mountainous land.

"I am fully aware of the difficulties the Russians had in Afghanistan," he said. "Our intelligence people and our State Department people are also fully aware."

He said it would be "very hard" to fight "a guerrilla war with conventional forces. And we understand that."

The deliberately vague reference to what groups the White House supports to replace the Taliban leaves open the question of whether Mr. Bush intends to provide aid to the rebel Northern Alliance, which has been conducting a stalemated war against the Taliban for years, or seek to restore the 86-year-old exiled Afghan king, Muhammad Zahir Shah.

He may choose both options. There is concern in the White House that too heavy a tilt toward the Northern Alliance would anger Pakistan, a critical but unstable American ally that is hostile to the rebels.

While some in the administration argue that the king, who has lived in Italy for more than a quarter century, would serve as a unifying force among Afghanistan's fractious tribes, he might also be regarded as a hapless puppet.

The Army Special Forces Command at Fort Bragg, N.C., has acknowledged that President Bush last week ordered its forces to deploy, but military and administration officials repeatedly refused to discuss any aspect of their operations.

Special operations, by their nature, are cloaked in secrecy and deception, making it impossible to know whether the officials who discuss them obliquely are being completely candid.

It was the legal doctrine of hot pursuit that the United States used to justify chasing Pancho Villa, the Mexican revolutionary commander, into Mexico in 1916, and to invade Cambodia in 1970 to pursue Vietcong forces.

Mr. Bush also announced today the release of $25 million in emergency food and medical aid for the refugees flowing out of Afghanistan and into Pakistan.

That aid, officials said, is intended to help alleviate the suffering, and to signal to Pakistan that the United States will not leave it to handle alone the flood of refugees that will likely accelerate once hostilities begin.

"This is the beginning of the aid, not the end," one official said. The United States has been the largest provider of humanitarian aid to Afghanistan, roughly $170 million this year. But the Taliban has ended air flights into and out of the country, crippling aid organizations, and it has harassed aid workers, many of whom have fled the country.

As the Pentagon has amassed a significant force in the region around Afghanistan, American military forces have already begun the difficult task of assembling intelligence on possible targets, including Mr. bin Laden's network and the Taliban government and military.

The Air Force has deployed high- flying U-2 surveillance aircraft to the region, apparently from Prince Sultan Air Base in Saudi Arabia. Secretary of Defense Donald H. Rumsfeld has acknowledged that an unpiloted American reconnaissance aircraft was lost over Afghanistan last weekend, but officials declined to say whether drones like it have continued to collect evidence.

One of the core missions of Army Special Forces is infiltrating enemy territory and reporting on enemy positions, targets and other intelligence information. The Army has five major Special Forces units, including the 5th Special Forces Group based at Fort Campbell, Ky., which has responsibility for the Persian Gulf region and has frequently trained there in recent years, including in Pakistan.

The White House spokesman, Ari Fleischer, declined to discuss the activities of American Special Forces or any "operational details" of the budding military campaign against those responsible for the attacks on Sept. 11.

He also declined to discuss what Mr. Bush meant by "hot pursuit."

The Pentagon continued to build up its forces, drafting still more deployment orders that involve additional troops and aircraft, though none have yet been issued, defense officials said.

The Pentagon also announced that Mr. Rumsfeld had authorized the Air Force to raise by 7,000 the number of National Guard and Reserve troops it can call to active duty, bringing the total to 20,000.

From all branches of the armed services, the Pentagon has now authorized the mobilization of 42,000 reserve troops.