(Bloomberg) -- More than two years after President Donald Trump quit the multinational nuclear deal with Iran, his administration is risking a crisis at the United Nations by threatening to reimpose international sanctions that were eased under that accord.

It’s a threat that could produce an outcome that once was unthinkable: pushing allies such as Germany and France to side with Russia and China in the UN Security Council, leaving the U.S. isolated.

The conflict may begin with a vote in the council as soon as Tuesday on a U.S. resolution to make permanent an international ban on arms deals with Iran that’s due to expire in October. If the UN fails to act, Secretary of State Michael Pompeo said in a tweet on Sunday, it “will make a mockery of its mission to maintain ‘international peace and security.”

Russia and China have threatened to exercise their veto power to kill the resolution. Diplomats say they don’t expect the U.S. will even muster the required nine votes in the 15-member council that would force them to do so.

“One way or the other, we won’t let the arms embargo expire,” U.S. Ambassador Kelly Craft said on a call with reporters last week. “Russia and China have a decision to make. They can be cosponsors of the No. 1 sponsor of terrorism, or they can do the right thing.”

People familiar with the matter, who asked not to be identified discussing private deliberations, said Security Council members still hoped to forestall a crisis through a compromise, perhaps by extending the arms embargo for a certain period, even if the initial resolution is rejected.

‘Snap Back’

The real flash point will come if efforts at compromise fail: Pompeo and Craft have said the U.S. can -- and will -- invoke a provision in the Iran accord that lets participants “snap back” UN sanctions that were eased in return for constraints on Iran’s nuclear program.

The result would be a significant expansion of the crippling sanctions on Iran that the U.S. already has imposed under the administration’s “maximum pressure” campaign. Less than three months before the U.S. presidential election, it would be a major escalation of U.S. pressure on Iran, much like the increasingly sharp measures the Trump administration has been taking against China.

“If the Trump administration takes this action and everyone else is on the other side of table, then the administration has once again isolated itself and it will fail,” said Wendy Sherman, who was lead negotiator on the Iran accord as undersecretary of state for political affairs under President Barack Obama and Secretary of State John Kerry.

When the accord between Iran, the U.S. and five other nations was announced in Geneva in 2013, Kerry emphasized the snapback as a safety net for the U.S. if Iran failed to keep its end of the agreement. It was offered as an assurance to members of the U.S. Congress skeptical that Iran would keep its end of the deal.

But Sherman says the U.S. gave up its right to trigger the mechanism when Trump quit what he’s called “the worst deal ever.” Trump has said the accord’s provisions intended to prevent Iran from developing a nuclear weapon expire too soon and the agreement fails to stop Iran’s development of ballistic missiles or its support for groups like Hezbollah.

‘Unilateral Proposals’

The prospect of the U.S. being isolated in the Security Council was laid bare when Pompeo made an online appearance in June to lobby member nations to support the U.S. move to extend the embargo on Iranian arms purchases and sales. While European countries agreed it’s problematic to let the embargo expire, they rejected the American snapback threat.

Europe will not “support unilateral proposals leading to the return of sanctions,” French Ambassador Nicolas de Riviere said during the meeting. “They would only deepen divisions in the Security Council and beyond and would not be likely to improve the situation on the ground of nuclear nonproliferation.”

One question is whether a U.S. snapback would prompt Iran to take further action to reject the terms of the nuclear deal. After initially staying within constraints of the accord despite the U.S. withdrawal, Iran has been revving up its nuclear program as European leaders proved unable to deliver on pledges to find ways to work around U.S. sanctions.

“By the time November elections come around, we could be dealing with a crisis” at the UN, said Ellie Geranmayeh, an Iran expert with the European Council on Foreign Relations. “We are going to be in a very, very perilous moment for the nuclear program.”

Iran’s leaders may wait to see whether Democrat Joe Biden defeats Trump in November’s election. Biden has signaled he’d open talks with Iran’s leaders.

“Iran would love to see me not be president,” Trump said at a news conference on Friday. But he predicted “if and when we win, we will make deals with Iran very quickly.”

Ayatollah Ali Khamenei, Iran’s supreme leader, last year ruled out talks, saying “negotiations are like a poison as long as the U.S. remains the same way it is.”

©2020 Bloomberg L.P.