Last month's hijacking of an Indian Airlines jet was most likely the work of a Muslim extremist group with ties to Pakistan's intelligence service, administration officials said yesterday.

Last week, U.S. envoys visited Islamabad to urge the country's military ruler, Gen. Pervez Musharraf, to end his government's support for the group, Harakat ul-Mujaheddin, as well as for Afghanistan's ruling Taliban, the radical Muslim movement that is harboring suspected terrorist Osama bin Laden.

The officials also urged Musharraf to cooperate with U.S. efforts to contain the spread of nuclear weapons and to hasten a return to civilian democratic rule in Pakistan, which ended last October with a coup against the elected prime minister, Nawaz Sharif.

Musharraf had a generally "positive" reaction to the American requests but did not commit to a timetable for severing ties with either the Taliban or Harakat ul-Mujaheddin, a senior administration official said.

U.S. officials will be judging Pakistan's progress on all fronts as they consider whether to include the country in President Clinton's itinerary when he travels to India and Bangladesh in late March, officials said. No U.S. president has visited South Asia since 1979. A stopover in Islamabad would have tremendous symbolic value to Pakistan, which faces growing international isolation because of its decision to test a nuclear device in 1998 and, more recently, the military coup.

A presidential snub, by contrast, would be a disaster for the new government.

"Our dilemma is that we can't do business as usual" with Pakistan's unelected leaders, a U.S. official said yesterday. "But to influence them on these issues, we have to engage them."

After the New York Times reported yesterday on the link between the hijacking and the Pakistani-backed group, President Clinton told reporters that "we do not have evidence that the Pakistani government was in any way involved in that hijacking." Pakistan's foreign ministry yesterday denied any role in the hijacking and called on India to produce whatever evidence it may have to support its repeated claims of Pakistani involvement.

According to a senior administration official, India already has shared intelligence that it believes proves Pakistani complicity, and U.S. officials are considering it. "Nothing can be ruled out," the official said. "If the smoking gun is found on the floor, we will point to it."

Solid proof of Pakistan's involvement would raise pressure on the State Department to add Pakistan to its list of countries that support terrorism. U.S. officials have been reluctant to take that step, partly because of Pakistan's role as a staunch Cold War ally--and staging area for the CIA-backed war to drive the Soviets from Afghanistan--and partly because they fear that further isolating Pakistan would be counterproductive.

On the other hand, U.S. officials have long been troubled by the relationship between Pakistan's Interservice Intelligence Division and the Harakat ul-Mujaheddin, a militant group fighting on Pakistan's side in the disputed Himalayan region of Kashmir. The organization, previously known as Harakat ul-Ansar, has been on the State Department's list of terrorist groups since 1997.

A senior official cited strong "circumstantial" evidence that the group was behind the hijacking, noting that the hijackers' demand for the release of Kashmiri militants from Indian jails echoed demands made by Harakat ul-Ansar when it kidnapped five Western tourists in 1995. The hijacking ended with the release of 155 hostages after the Indian government freed three members of the militant group.

Pakistan's support for the group was one of several items on the agenda during last week's meeting between Musharraf and the three American envoys--Karl F. Inderfurth, the assistant secretary of state for South Asia, Michael Sheehan, the State Department's counterterrorism chief, and Donald Kamp, the South Asia specialist on the National Security Council.

"What we have asked is for General Musharraf to lay out a more comprehensive road map so we can see where he is heading," a senior official said, adding, "He did not rebuff us on the terrorism issue. He said he would consider the administration's requests to deal with these organizations of concern to us."

The American delegation got more satisfaction on the democracy issue. Musharraf promised to allow local elections soon, followed by provincial and national elections at a later date, the official said.

"We did not go there to warn Pakistan about what kind of punishment" the country might face, the official said, adding that "no conditions" have been attached to a presidential visit. "It was an attempt to lay out our concerns."

CAPTION: Maulana Masood Azhar, right, a Muslim leader who was one of the prisoners released by India last month in exchange for 155 passengers and crew of hijacked plane, walks with unidentified men at the Karachi airport last week.