WASHINGTON — Even as Susan E. Rice took to the Sunday talk shows last month to describe the Obama administration’s assessment of the Sept. 11 attack on the American diplomatic mission in Benghazi, Libya, intelligence analysts suspected that the explanation was outdated.

Ms. Rice, the United States ambassador to the United Nations, has said that the judgments she offered on the five talk shows on Sept. 16 came from talking points prepared by the C.I.A., which reckoned that the attack that killed Ambassador J. Christopher Stevens and three other Americans had resulted from a spontaneous mob that was angry about an anti-Islamic video that had set off protests elsewhere. That assessment, described to Ms. Rice in briefings the day before her television appearances, was based on intercepted communications, informants’ tips and Libyan press reports, officials said.

Later that Sunday, though, American intelligence analysts were already sifting through new field reports that seemed to contradict the initial assessment. It would be several days, however, before the intelligence agencies changed their formal assessment based on those new reports, and informed administration officials about the change. Intelligence officials say such a lag is typical of the ever-changing process of piecing together shards of information into a coherent picture fit for officials’ public statements.

Gov. Mitt Romney and Congressional Republicans have sharply criticized Ms. Rice’s comments and the administration’s shifting public positions on the cause of the attack, criticisms that Mr. Romney will probably reprise in the final presidential debate on Monday night.