UNITED NATIONS (AP) — The Trump administration on Thursday formally notified the United Nations of its demand for all U.N. sanctions on Iran to be restored, citing significant Iranian violations of the 2015 nuclear deal.

Secretary of State Mike Pompeo delivered the notification to the president of the U.N. Security Council, setting the stage for a showdown in the world body that could lead to a crisis of credibility for its most important and powerful institution. Even before Pompeo presented the council president with the notice, other members rejected the step.

None of the other council members believe the U.S. has the legal right to demand the re-imposition, or “snapback,” of sanctions because President Donald Trump withdrew from the nuclear deal in 2018. As such, the demand is expected to further isolate the U.S. at the U.N. and test the Security Council’s credibility.

In a letter presented to Indonesia’s ambassador to the U.N., Dian Triansyah Djani, whose country currently holds the rotating presidency of the council, Pompeo said the U.S. was notifying the body of “significant non-performance” by Iran related to the nuclear deal. As a result, Pompeo said the process leading to the re-imposition of U.N. sanctions had been initiated.

The U.N.’s nuclear watchdog, the International Atomic Energy Agency, has reported some Iranian violations of the agreement, but Tehran says those are the result of the U.S. violating the accord by withdrawing from it and then re-imposing harsh unilateral sanctions.

Pompeo noted that the European participants in the deal had attempted to bring Iran back into compliance. But he said “despite extensive efforts and exhaustive diplomacy on the part of those member states, Iran’s significant non-performance persists.”

“As a result, the United States is left with no choice but to notify the council that Iran is in significant non-performance of its JCPOA commitments,” Pompeo wrote, using the acronym for the deal’s formal name, the Joint Comprehensive Plan of Action.

Pompeo’s letter was accompanied by a six-page explanation of why the U.S. believes it retains the right to invoke snapback, a mechanism afforded to participants in the nuclear accord by the Security Council resolution that enshrined the deal.

The U.S. maintains that its withdrawal from the nuclear deal does not obviate its right as an original participant and a permanent Security Council member to demand the restoration of sanctions.

That argument, however, has already been rejected by the other members of the council, including U.S. allies Britain and France, along with China and Russia.