And should former Vice President Joseph R. Biden Jr. win in November, the resumption of sanctions will make it more complicated to reassemble some version of the agreement. Mr. Biden would have to reverse the move, making it appear he had made a concession to Iran even as it has resumed work on its nuclear program in reaction to Mr. Trump’s decision to abandon the deal.
But for the president’s critics, the move underlines how his administration has splintered alliances and fractured understandings with the United States’ superpower adversaries, Russia and China. They had been unified in reaching the 2015 agreement. Now the United States has gone its own way, and Russia and China seem poised to resume conventional weapons sales to Iran next month when an arms embargo against Iran expires, over the objections of Washington.
“The irony I see here is that Trump is actually doing the U.N. and multilateralism a big favor, because by invoking the snapback, he is putting on display that the kind of clumsy unilateralism that he is known for doesn’t work,” said Ian Johnstone, a professor of international law at the Fletcher School at Tufts University.
He predicted the sanctions would not be enforced by other countries and would be “met with a collective shrug.”
“The U.S. will insist that the sanctions are back on and most other countries will say, ‘No, they’re not,’” said Mr. Johnstone, who advised Kofi Annan, the former United Nations secretary general.
In fact, the Trump administration’s insistence on reimposing the original United Nations sanctions, which had been formulated during the Bush and Obama administrations to force Tehran to the negotiating table, means that the United States alone will enforce them. That has raised doubts over whether the sanctions will bring much, if any, additional economic pain; one Security Council diplomat compared the American saber-rattling to pulling the trigger of an unloaded gun.
Administration officials disagree. In his statement on Saturday, Mr. Pompeo rapped the Security Council for refusing to extend a global arms embargo against Iran that is set to expire on Oct. 18. Only the Dominican Republic voted with the United States, and Mr. Pompeo made clear that the American demand to snap back the broader sanctions was in direct response to the arms embargo being allowed to expire, under the terms of the nuclear accord.