As its crude exports slump and economic meltdown looms Iran has called on the EU to ‘uphold its obligations’ under the 2015 nuclear deal. But a restart of EU crude buying is unlikely; even takings by key customer China may be hostage to US trade talks.

Even Iran’s phlegmatic foreign minister Mohammad Javad Zarif looks to have run out of patience. One year on from the unilateral US abrogation of the 2015 nuclear deal known as the JCPOA, Iran has given the deal’s three...