That visit was the beginning of a more aggressive effort by the administration to pressure Pakistan’s government into stepping up its fight. The decision last year to draw up the Pentagon order authorizing for a Special Operations campaign in the tribal areas was part of that effort.

But the fact that the order remains unsigned reflects the infighting that persists. Administration lawyers and State Department officials are concerned about any new authorities that would allow military missions to be launched without the approval of the American ambassador in Islamabad. With Qaeda operatives now described in intelligence reports as deeply entrenched in the tribal areas and immersed in the civilian population, there is also a view among some military and C.I.A. officials that the opportunity for decisive American action against the militants may have been lost.

Pakistani military officials, meanwhile, express growing frustration with the American pressure, and point out that Pakistan has lost more than 1,000 members of its security forces in the tribal areas since 2001, nearly double the number of Americans killed in Afghanistan.

Some architects of America’s efforts in Pakistan defend the Bush administration’s record in the tribal areas, and vigorously deny that Washington took its eye off the terrorist threat as it focused on Iraq policy. Some also question whether Mr. bin Laden and Mr. Zawahri, Al Qaeda’s top two leaders, are really still able to orchestrate large-scale attacks.

“I do wonder if it’s in fact the case that Al Qaeda has really reconstituted itself to a pre-9/11 capability, and in fact I would say I seriously doubt that,” said Mr. Crocker, the American ambassador to Pakistan between 2004 and 2006 and currently the ambassador to Iraq.

“Their top-level leadership is still out there, but they’re not communicating and they’re not moving around. I think they’re symbolic more than operationally effective,” Mr. Crocker said.

But while Mr. Bush vowed early on that Mr. bin Laden would be captured “dead or alive,” the moment in late 2001 when Mr. bin Laden and his followers escaped at Tora Bora was almost certainly the last time the Qaeda leader was in American sights, current and former intelligence officials say. Leading terrorism experts have warned that it is only a matter of time before a major terrorist attack planned in the mountains of Pakistan is carried out on American soil.