Updated

The Central Intelligence Agency is racing to deal a death blow to Al Qaeda while the network is weakened, raising concerns for some U.S. officials that the campaign of drone strikes could become so politically damaging for Pakistan's leaders that they may seek to curtail them.

U.S. officials said over the weekend that a CIA drone strike killed Al Qaeda's second in command on Aug. 22, a major blow to militants in their country and a sign that American officials are pushing to slam the network while its fortunes are down.

But the strike stoked Pakistani anger over the U.S.'s aggressive unilateral pursuit of militants in their country, revealing the double-edged nature of the current drone program in which each U.S. victory takes a toll on the U.S.-Pakistani relationship. Several senior U.S. officials said there was growing fear that Pakistani leaders could move to curtail the flights in response to outcries from the Pakistani public, which believes the strikes kill civilians. U.S. officials say militants—not civilians—are killed.

The killing of Attiyah Abd al-Rahman, who was effectively Al Qaeda's chief operating officer, in the rugged mountains of Waziristan bordering Afghanistan, "seriously weakens Al Qaeda," said Seth Jones, an Al Qaeda specialist at Rand Corp., a think tank. "It doesn't push them to irrelevancy, but it probably pushes them closer to strategic defeat."

Mr. Rahman oversaw attack planning for the group, and some officials believe he played a more hands-on role than Osama bin Laden, who was killed by U.S. Navy SEALs in a unilateral mission deep inside Pakistan in May.

U.S. officials believe Mr. Rahman will be difficult to replace due to his unique operational role and close ties to affiliated groups, but say they are now monitoring Al Qaeda's leaders to see how they seek to regroup and whether fractures develop.

Despite bilateral efforts to rebuild trust between the U.S. and Pakistan in the wake of the bin Laden raid, officials say Pakistan played no direct role in the operation that eliminated Mr. Rahman, underlining the poor state of U.S.-Pakistan cooperation.

A Pakistani defense official expressed frustration that Washington didn't consult with Pakistan before launching the strike.

"They tell us we have to act like allies. Always there are lectures and demands," said the Pakistani defense official. "But they don't treat us like allies."

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