WASHINGTON &

The top U.S. military officer Friday described the air strike that killed a high-ranking al-Qaida commander in Pakistan as an important victory, but he refused to say whether the U.S. government had anything to do with it.




"The strike was a very important one, it was a very lethal one," Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said at a Pentagon news conference. He brushed aside questions about any role the Pentagon played in it.




The CIA and the Pakistan government also refused to say who might have fired the missile or missiles that are believed to have killed Abu Laith al-Libi and perhaps some other al-Qaida leaders in a small compound in northwest Pakistan earlier this week.




The U.S. government's reluctance to take public credit for killing of Libi underscores the growing tensions between the United States and Pakistan over how to attack al-Qaida as it entrenches itself on the territory of the key U.S. ally, current and former U.S. officials and other experts said.




Pakistan won't allow U.S. forces onto its soil to conduct counter-terrorism missions, so Washington has resorted to air strikes launched from across the border in Afghanistan. But despite the occasional success, few in the counter-terrorism community believes that air strikes are enough, and some have been openly pressing for more access.




In recent weeks, Director of National Intelligence Michael McConnell and CIA Director Michael V. Hayden made a trip to Pakistan to press for more cooperation from military and intelligence officials there. And Friday, Mullen said he, too, will be traveling to Islamabad later this month to meet with Pakistani leaders, including the army chief, Gen. Ashfaq Kiani.




"While this particular strike was very successful, and we were very pleased with the outcome, there is still a great deal more work to do," Mullen said.




Mullen said the U.S. government remains "concerned about the safe havens" in the tribal areas, a concern heightened by an increase in al-Qaida and Taliban violence against targets inside Pakistan in recent months.




"Being able to have an impact in a safe haven, I think, is an important one," Mullen said. "We're very committed to working with the Pakistanis on this."




He acknowledged that the United States remains essentially powerless to do anything within Pakistan without the government's cooperation. He said he hoped to establish a personal relationship with Kiani and the rest of the Pakistan leadership and to "make sure that I understand his concerns and in fact work very hard to support them. ... We will only do what is requested by Pakistan."




President Pervez Musharraf has insisted that Pakistani forces are capable of defeating al-Qaida, the Taliban and other militants in the tribal areas. He has remained silent on Libi's death, which was announced this week on some al-Qaida-affiliated Web sites.




Local officials had said about 12 people were killed in the strike late Monday or early Tuesday, most of them "foreigners" &

Arabs and Central Asians, which fits the profile of al-Qaida fighters present in the tribal areas.




Residents had reported a missile strike on the small compound just outside Mir Ali, which is considered a militant stronghold. Witnesses said they heard what they believed were Predator drones flying in the area shortly before the compound was hit.




Bruce Riedel, a veteran Pakistan expert with the CIA, State Department and National Security Council, said the silence surrounding who was behind the air strike was designed to hide the fact that the United States is being forced to fight al-Qaida at a distance without the full support of the Pakistan government.




"That no one seems to be responsible shows just how delicate and fragile our relationship ... with Pakistan is," Riedel said. He said the situation has deteriorated significantly in recent months, as the United States grows more concerned with the spread of Taliban militants, the assassination of former Prime Minister Benazir Bhutto and the Musharraf government's preoccupation with winning upcoming parliamentary elections.




"We are now seeing a huge al-Qaida and Taliban presence in Pakistan, and a Pakistan government that is not capable of dealing with it itself, and is reeling because of its own domestic political problems, and we have to resort to fighting it indirectly through unacknowledged Predator strikes. That is far from an optimal way of going about it," said Riedel, who is now a South Asia expert and senior fellow at the Brookings Institution, a centrist Washington think tank.




Lisa A. Curtis, who also was a Pakistan expert at the CIA, the State Department and the Senate Foreign Relations Committee, said the silence was understandable given that a large percentage of the Pakistani people have said they opposed their government's cooperation with the United States on counter-terrorism.