President Donald Trump said he would call on the UN Security Council to restore all nuclear-related sanctions on Iran, an attempt to kill off the 2015 nuclear agreement and force Tehran back to the negotiating table.

“Mark it down, Iran will never have a nuclear weapon,” Trump said at a White House news conference on Wednesday. “We paid a fortune for a failed concept, a failed policy that would have made it impossible to have peace in the Middle East.”

The move sets the Trump administration on a collision course with other world powers who say the U.S. doesn’t have the authority to reimpose international sanctions and that they won’t go along. U.S. Secretary of State Michael Pompeo will formally propose the “snapback” of sanctions Thursday at the United Nations.

While many nations are wary of Iran, the U.S. has been almost totally isolated at the UN in its most recent efforts to raise pressure on the Islamic Republic, abandoned by even close allies such as France and the U.K. Building a coalition may be even harder now for Trump, who’s trailing in opinion polls less three months before the presidential election.

Sergei Ryabkov, Russia’s deputy foreign minister, said the U.S. actions would fail, according to Interfax. Russia, a close ally of Tehran, condemns a move that will lead to a “deep crisis in the UN Security Council,” he said.

An effort last week to extend indefinitely a 13-year-old arms embargo on Iran was defeated in historic fashion: 11 members of the Security Council abstained, with just the Dominican Republic joining the U.S. as China and Russia vetoed the measure.

“Because the Trump administration has been so unilateral in its approach to Iran even among its allies, it doesn’t have any support for implementing a multilateral strategy,” said Rodger Shanahan, a research fellow specializing in Middle East security issues at the Lowy Institute in Sydney. “There is a good chance that the Trump administration won’t be around after the November election, so why would the UN and its allies even push for a vote.”

The State Department referenced the previous Security Council rebuke in a statement after Trump spoke.

“Secretary Pompeo’s notification to the Council follows its inexcusable failure last week to extend the arms embargo on the world’s leading state sponsor of terrorism and anti-Semitism,” the State Department said. It added that the snapback would extend the arms embargo by default.

The president has long called the agreement the “worst deal ever” and has said he wants a new accord to help foster peace across the Middle East. His administration has used increasingly tough economic and diplomatic pressure to try to convince European allies to quit the 2015 nuclear deal, saying Iran used the revenue it got from eased sanctions to finance conflicts from Syria to Yemen.

European allies supportive of the nuclear deal struggled to find a way around the U.S. restrictions, depriving Iran of investment and causing its currency to plunge.

Iranian President Hassan Rouhani’s government ruled out any talks in response to what it calls “blackmail.” On Thursday, the Islamic Republic unveiled two new missiles, including one named after Qassem Soleimani, the top Iranian general killed in a U.S. drone strike.

Under the “snapback” process outlined in the 2015 nuclear deal, the Security Council has 30 days to vote on a resolution to continue Iran’s sanctions relief, a move the U.S. could then proceed to veto. If such a resolution isn’t adopted, UN sanctions eased in return for constraints on Iran’s nuclear program would theoretically be restored, effectively killing the accord.

The process, as enshrined in a UN resolution, appears straightforward. But every other party to the deal, including China and America’s European allies, argue that snapback was a right given to the deal’s participants, and since the U.S. withdrew, its actions would be invalid.

The U.S. “is not in any position to ask the Security Council to snap back the sanctions,” Chinese Foreign Ministry spokesman Zhao Lijian said Thursday in Beijing. He said China “firmly opposes” unilateral sanctions and urged the U.S. to “respect the legitimate rights and interests of all other countries.”

The U.S. has a different legal interpretation, arguing that UN Resolution 2231 lists it as a participant for purposes of snapping back sanctions.

Pompeo vowed to hold countries like Russia and China accountable, if they refused to go along with the U.S. declaration that the nuclear deal was void and, instead, move ahead with sales of advanced weapons to Iran once the arms embargo expires in October.

Debate Since 2015

Supporters of the agreement say it took Iran off a path toward nuclear weapons. But critics said it provided Iran with economic benefits in the short-term without any long-term guarantee the country wouldn’t eventually decide to restart its nuclear program.

International Atomic Energy Agency inspectors repeatedly affirmed that the Iranians were abiding by the accord before the U.S. withdrew. As Washington reimposed sanctions, Iran abandoned parts of the agreement, stockpiling enriched uranium beyond agree upon levels, saying it would reverse course if the U.S. returned to the deal.

The dispute between the U.S. and the rest of the permanent members of the Security Council could plunge the body into a crisis with no clear path toward a resolution.

“It will be one of the worst crises to face the UN Security Council in a generation,” said Richard Nephew, who was the lead sanctions expert for the Obama administration team that negotiated the accord. “The council will be hopelessly divided, without any clarity on how to move forward.”