For nearly two years the United States has tried and failed to negotiate a revival of the 2015 Iran nuclear deal yet Washington and its European allies refuse to close the door to diplomacy.
Their reasons reflect the danger of alternative approaches, the unpredictable consequences of a military strike on Iran, and the belief that there is still time to alter Tehran's course: even if it is inching toward making fissile material it is not there yet, nor has it mastered the technology to build a bomb, according to officials.
