The White House’s top adviser on Afghanistan and Pakistan said Friday that taking out three to five key al Qaeda leaders could amount to a ”knockout punch” against the group.

Speaking at the Aspen Security Forum, retired Lt. Gen. Douglas Lute said now is the time to keep up US counterterrorist actions in Pakistan, even if they upset the Pakistani government.

Lute said killing al Qaeda successor Ayman al-Zawahri and four of his lieutenants in the next six months could ”significantly jeopardize al Qaeda’s capacity to regenerate.”

His comments came in response to former US intelligence chief Dennis Blair, who said that the US should stop its drone campaign in Pakistan. The CIA’s unmanned aircraft operation aimed at al Qaeda is backfiring by damaging the US-Pakistan relationship, he said.

The program, which targets Pakistani-based al Qaeda and other militants, has jumped from fewer than 50 in the Bush administration, to more than 200 strikes in Pakistan’s ungoverned tribal areas since President Barack Obama took office. Strikes are carried out with tacit Pakistani assent, by drones that fly from Afghanistan.

Publicly, Pakistani officials decry the hits. That tension grew worse after the US unilateral raid into Pakistan on May 2 to kill al Qaeda leader Osama bin Laden and an earlier incident, in January, when a CIA contractor was held for killing two Pakistani men in Lahore whom he said were trying to rob him.

Pakistan’s ambassador Husain Haqqani acknowledged the drone strikes, but said his government was pushing for a reduction because they’d begun to fray public support.

”Part of the agreement is neither side is going to talk too much about the drone strikes,” he said. ”They’ve taken out many people who needed to be taken out but if the cost is if support for the overall war starts to decline, you have to take that into account.”

Blair suggested that now is the time to give Pakistan more say in what gets hit by drone strikes and when, despite Pakistan’s record of tipping off militants when it gets advance word of US action.

”We should offer the Pakistanis to put two hands on the trigger,” he said, as well as encourage them to send more troops to the ungoverned areas, to challenge the militants.

Blair said the continuing drone strikes are more of a nuisance than a real threat to al Qaeda, and that only a ground campaign by Pakistan would truly threaten it and other militant organizations. The US had been training forces for that purpose until the program was canceled by Pakistan in retaliation for the raid to kill bin Laden.

Al Qaeda ”can sustain its level of resistance to an air-only campaign,” Blair said. ”I just see us with that strategy walking out on a thinner and thinner ledge and if even we get to the far end of it, we are not going to lower the fundamental threat to the US any lower than we have it now.”

Lute countered: ”This is a period of turbulence in an organization which is our arch enemy. This is a period, therefore, that all military doctrine suggests you need to go for the knockout punch.”

Other conference speakers agreed, including Bush administration veteran Fran Townsend, the former chief counterterrorism adviser in the White House.

”This has been the key tool in degrading the al Qaeda leadership,” Townsend said. Without it, she said, al Qaeda would be a far greater threat to the US Stephen Hadley, former national security adviser to President George W. Bush, said the Pakistani government in the past had assented to the strikes, if they were used against major targets.

”The line they drew was boots on the ground, special (operations) forces in Pakistan,” Hadley said. ”We did a limited cross-border operation and it caused a huge outcry to the point where we said we’re not going to do that anymore” unless it was to get bin Laden or his then-deputy Ayman al-Zawahri, ”knowing you’re going to pay in Pakistan public opinion. And we did” after bin Laden was killed.

Blair, who was forced to resign by the Obama administration, says the White House undermined his authority as director of national intelligence by siding with the CIA, instead of telling it to listen to him.

”They sided enough with the CIA in ways that were public enough that it undercut my position,” he said.