U.S. counterterrorism officials are increasingly convinced that the killing of Osama bin Laden and the toll of seven years of CIA drone strikes have pushed al­Qaeda to the brink of collapse.

The assessment reflects a widespread view at the CIA and other agencies that a relatively small number of additional blows could effectively extinguish the Pakistan-based organization that carried out the Sept. 11, 2001, terrorist attacks — an outcome that was seen as a distant prospect for much of the past decade.

U.S. officials said that al-Qaeda might yet rally and that even its demise would not end the terrorist threat, which is increasingly driven by radicalized individuals as well as aggressive affiliates. Indeed, officials said that al­-Qaeda’s offshoot in Yemen is now seen as a greater counterterrorism challenge than the organization’s traditional base.

President Obama has steadily expanded the clandestine U.S. campaign against that Yemen group, most recently by approving the construction of a secret Persian Gulf airstrip for armed CIA drones. But recent setbacks, including a botched U.S. military airstrike on American-born radical cleric Anwar al-Aulaqi, underscore the difficulties that remain.

Nevertheless, the top U.S. national security officials now allude to a potential finish line in the fight against al-Qaeda, a notion they played down before bin Laden was killed by U.S. forces in a May 2 raid in Pakistan.

Defense Secretary Leon E. Panetta declared during a recent visit to Afghanistan that “we’re within reach of strategically defeating al-Qaeda.” The comment was dismissed by skeptics as an attempt to energize troops while defending the administration’s decision to wind down a decade-old war.

But senior U.S. officials from the CIA, the National Counterterrorism Center and other agencies have expressed similar views in classified intelligence reports and closed-door briefings on Capitol Hill, officials said.

“There is a swagger within the community right now for good reason,” said Sen. Saxby Chambliss (Ga.), the ranking Republican on the Senate intelligence committee.

“Al-Qaeda in the Arabian Peninsula is nowhere near defeat,” Chambliss said, referring to the Yemen-based affiliate. “But when it comes to al-Qaeda [core leadership in Pakistan], we have made the kind of strides that we need to make to be in a position of thinking we can win.”

Even those who winced at Panetta’s word choice agree with his broader observation. “I’m not sure I would have chosen ‘strategic defeat,’ ” said a senior U.S. counterterrorism official, who cautioned that even if al-Qaeda is dismantled, its militant ideology has spread and will remain a long-term threat.

“But if you mean that we have rendered them largely incapable of catastrophic attacks against the homeland, then I think Panetta is exactly right,” the official said, speaking on the condition of anonymity to discuss sensitive intelligence. “We are within reach of rendering them to that point.”

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