Iran’s recent breach of the limits that the agreement had placed on its uranium enrichment has raised fears that it could be close to building an atomic bomb. London, Paris and Berlin want to prevent that via diplomatic means while also keeping the United States on their side.

But striking that balance could be difficult, partly because American officials believe the sanctions they imposed on Iran after the U.S. left the nuclear deal — and which Tehran wants lifted as a precondition for fresh talks — are working.

Another angle: A key Democratic senator said on Tuesday that at least four Republicans in the Republican-controlled chamber would break ranks to support a measure — prompted by the American killing of Tehran’s top general — that would force President Trump to win congressional authorization before taking further military action against Iran. It will likely face a presidential veto.

Yesterday: President Hassan Rouhani of Iran called for a special court to examine the recent downing of a Ukrainian passenger jet by the Iranian military.

Closer look: Security camera footage verified by The Times shows that two missiles fired 30 seconds apart took down the plane, killing all 176 people aboard.