“Based on our understanding of the Iranian system and the history of I.R.G.C. operations, the intelligence community assesses that activity this extensive on the part of the Quds Force would not be conducted without approval from top leaders in Iran,” a senior intelligence official said, referring to the Islamic Revolutionary Guard Corps. Intelligence officials have cast this view as an “assessment,” a logical inference based on years of studying the Revolutionary Guard.

But some senior American officials are hesitant to make this deductive leap. Twice during his recent trip through Asia, Gen. Peter Pace, the chairman of the Joint Chiefs of Staff, broke with military officials in Baghdad and said he was not ready to conclude that Iran’s top leaders were behind the attacks.

During a stopover in Jakarta, Indonesia, General Pace told reporters that American forces had confirmed that some bomb materials found inside Iraq were made in Iran, but “that does not translate that the Iranian government, per se, for sure, is directly involved in doing this,” he said, The Associated Press reported.

There is a larger lesson about the way intelligence analysis is carried out. Intelligence officials say that while forensic analysis can determine how a weapon is engineered and where its components are manufactured, the hardest task they face is discerning the strategy and intent of a hostile government.

Last month, Senator John D. Rockefeller IV of West Virginia, the Democratic chairman of the Senate Intelligence Committee, said during an interview that the United States still had far too few intelligence resources inside Iran to draw any conclusions about the intent of senior Iranian leaders.