The officials also cited lapses and misjudgments that were not disclosed in the declassified government report released Jan. 7 about what went wrong inside the nation’s counterterrorism network.

In September, for example, a United Nations expert on Al Qaeda warned policy makers in Washington that the type of explosive device used by a Yemeni militant in an assassination attempt in Saudi Arabia could be carried aboard an airliner.

In early November, American intelligence authorities say they learned from a communications intercept of Qaeda followers in Yemen that a man named “Umar Farouk” — the first two names of the jetliner suspect, Umar Farouk Abdulmutallab — had volunteered for a coming operation.

In late December, more intercepts of Qaeda operatives in Yemen, who had previously focused their attacks in the region, mentioned the date of Dec. 25, and suggested that they were “looking for ways to get somebody out” or “for ways to move people to the West,” one senior administration official said.