At Foreign Policy, Mark Hibbs, the reporter who helped break the AQ Khan-nuclear black market story and is now with the Carnegie Endowment, writes:

The International Atomic Energy Agency’s newest report on Iran’s nuclear program … brings forth evidence that the Islamic Republic has covered a lot of technical ground to develop a nuclear weapon over the past two decades. But it stops short of the most incendiary charge: that Iran’s political leadership masterminded a secret program to possess atomic arms. In view of the wealth of incriminating detail that the IAEA presented in the report, that omission may be the only face-saving argument left to Tehran to permit diplomacy to continue as usual. And because the report draws no conclusions about how far along Iran’s nuclear weapons program is, it will be irrelevant to Israel’s calculus of whether to attack Iranian nuclear installations.” [Emphasis added.]

In other words

… the IAEA report should certainly not be considered a casus belli.