The Obama administration has called the negotiations to curb Iran’s nuclear capabilities a critical test of the Tehran regime’s intentions. The dilemma is that through its mastery of uranium enrichment, Iran has achieved a breakout option: centrifuges ostensibly intended to produce low-enriched uranium for civil use can be kept spinning to yield high-enriched uranium for bomb-making. Negotiations can narrow, but not eliminate that inherent ambiguity, since any country that crosses that key technological threshold is a “virtual” nuclear-weapons state, according to International Atomic Energy Agency chief Mohamed ElBaradei.

For the Tehran regime, a hedge has political utility as a source of leverage with its regional neighbours and as a complicating factor in the strategic calculations of its adversaries. For the Obama administration, the question is how much ambiguity it is prepared to live with.