(24.02.) Iran’s efforts to hide its nuclear facilities and to deceive the West about its activities have also intensified doubts. But some American analysts warn that such behavior is not necessarily proof of a weapons program. They say that one mistake the C.I.A. made before the war in Iraq was to assume that because Saddam Hussein resisted weapons inspections — acting as if he were hiding something — it meant that he had a weapons program.

As Mr. Kay explained, “The amount of evidence that you were willing to go with in 2002 is not the same evidence you are willing to accept today.”