Iran's Nuclear Technology: Is There a Threat of War?

The UN's International Atomic Energy Agency is reporting "serious concerns" about Iran's ability to build an atomic bomb. There's still no evidence that it wants to. But it's still trying to develop technology that's only useful for nuclear weapons, and that it has enough enriched uranium to fuel a small arsenal, if it chooses to build one. It's also moving more projects to a chamber under a mountain. In Israel, there's public debate over whether it's time to attack. Is that likely? Would the US become involved?  Will Iran engage in diplomacy if it faces a tough new round of economic sanctions?