Tehran, Sept. 28 -- Iran's foreign minister, Abbas Araghchi, has formally told the United Nations that any attempt to revive Security Council sanctions terminated under Resolution 2231 is illegitimate, a statement that lays bare a widening rift between Western capitals and the remaining signatories to the 2015 nuclear deal and sets the stage for a new phase of diplomatic confrontation.

In a letter circulated in New York and addressed to UN Secretary-General Antonio Guterres and the Security Council president, Araghchi said Tehran "firmly rejects the alleged reinstatement of resolutions terminated under resolution 2231." The message, dispatched as capitals traded accusations over process and blame, reflects Iran's view that the so-called ...