For his part, Mr Obama has made it clear that he would countenance war only if Iran were building a nuclear weapon, which his intelligence chiefs do not now think is the case.

ECONOMIST: Iran

We now know enough to be reasonably confident that such action would have led to nuclear war.

BBC: The speeches written but never given

Nuclear deterrence, this school of thought asserts, was shown to work globally in the cold war and can now be expected to work regionally.

ECONOMIST: The ostrich��s view of the world

Cartwright has described that system, now entering its second study phase, as a key component in transforming the aging Cold War nuclear weapons stockpile.

CENTERFORSECURITYPOLICY: STRATCOM: Safe, reliable deterrence critical