Pence made the promise, to cheers, during his address to the annual conference of the American Israel Public Affairs Committee in Washington, D.C. Monday night. Signed in 2015 by Iran, the United States and a group of other countries, the Iran deal curbs Iran’s nuclear program in response for relieving sanctions.

President Donald Trump opposes the deal. In October, he declined to certify that Iran was complying with it. But he has yet to fully withdraw the United States from the accord, instead asking Congress to pass legislation altering it.

But Pence told AIPAC Monday that this was the deal’s “last chance,” and that if it is not amended, Trump will withdraw from it.

“Earlier this year, the president waived sanctions to give our lawmakers and our allies time to act,” Pence said. “But make no mistake about it: This is their last chance. Unless the Iran nuclear deal is fixed in the coming months, the United States of America will withdraw from the Iran nuclear deal.”

Pence, like several of the other speakers Monday, praised Trump for recognizing Jerusalem as Israel’s capital and vowing to move the United States embassy there in May. Pence also praised the administration for weakening ISIS, supporting Israel in international forums and giving Israel a large security aid package.

Pence called Trump “the most pro-Israel president in American history,” but not before slipping up and accidentally calling him “the most pro-life” president. He also ended his speech by quoting the “shehechiyanu” blessing, which Jews recite on special occasions.

“Thanks to the president’s leadership, the alliance between America and Israel has never been stronger,” Pence said. “America stands with Israel today, tomorrow and always.”

Also speaking Monday night was U.S. Ambassador to the United Nations Nikki Haley, a crowd favorite who sprinkled her speech with one-liners that drew 12 standing ovations. She repeated the promise that the United States would tie foreign aid to countries’ voting records in the U.N. — though she added that would be one of several considerations.

“That should be one of the factors, and we are determined to start making that connection” between foreign aid and U.N. votes, Haley said. “Some people accuse us of showing favoritism toward Israel. There’s nothing wrong with showing favoritism toward an ally.”

Senator Chuck Schumer, the Democratic minority leader, also hit key crowd-pleasing notes in his speech, which he peppered with Hebrew words. Also speaking were Rep. Kevin McCarthy, the Republican majority leader, Rep. Nancy Pelosi, the Democratic minority leader and Steny Hoyer, the Democratic minority whip.

Israeli Prime Minister Benjamin Netanyahu will address the conference on Tuesday.