Mr. Trump, officials said, would not waive the sanctions again in May unless the Europeans agreed to a “follow-on” deal that eliminates the “sunset clauses” in the current agreement, under which Iran is allowed to resume activities like enriching uranium. It would also have to contain “triggers,” including inspections of Iranian facilities, which would lead to a reimposition of sanctions if Iran failed to comply.
Iran did not immediately react to the announcement, though officials said they were prepared if Mr. Trump had decided to act. Iran’s first vice president, Eshagh Jahangiri, told the semiofficial ISNA news agency, “If the Americans withdraw from the nuclear deal, we will not hold a mourning service; we are fully prepared for any likely event.”
White House officials played up the sanctions against Mr. Larijani as a symbol of Mr. Trump’s displeasure with the Islamic Republic’s government — and solidarity with those who are rallying against it. They predicted that the move would reverberate politically inside Iran, since Mr. Larijani’s brother, Ali Larijani, is the head of Iran’s parliament.
Mr. Trump’s decision came after a Thursday meeting with his national security team on a turbulent day, during which he made a vulgar reference to immigrants in a meeting with senators and told The Wall Street Journal, “I probably have a very good relationship with Kim Jong-un,” referring to the North Korean leader.
Starting on Friday, Mr. Trump faces a series of deadlines related to the Iran nuclear deal and sanctions that were waived as a result of it. The first of those deadlines — for extending or terminating the waiver for the central bank and oil sanctions — is by far the most significant.
In October, Mr. Trump refused to certify the agreement — a decision he is expected to reaffirm next week. At the time, the president warned that he would take further action to nullify the deal if Congress and the allies did not act.
“In the event we are not able to reach a solution working with Congress and our allies,” he said, “then the agreement will be terminated.”
Republicans in the Senate have drafted legislation that would amend the deal by eliminating its “sunset provisions.” But they have so far been unable to bridge gaps with the Democratic caucus.
There is also no evidence that the Europeans have the appetite to reopen the deal.
On Thursday, hours before Mr. Trump made his decision, European foreign ministers met in Brussels with Iran’s foreign minister, Mohammad Javad Zarif, ostensibly to press Tehran about its destabilizing activities in the region, which are putting the nuclear deal at risk.
But to some in Washington, the meeting amounted to a show of unity between Europe and Iran — and of defiance toward the United States. There were images of a smiling Mr. Zarif, seated among smiling European officials, followed by a parade of statements in favor of the deal.
“I don’t think anybody has so far produced a better alternative,” said the British foreign secretary, Boris Johnson. “The Iran nuclear deal makes the world safer. European partners were unanimous today in our determination to preserve the deal and tackle Iran’s disruptive behavior.”
The European Union’s foreign affairs chief, Federica Mogherini, said, “The deal is working — it is delivering on its main goal, which means keeping the Iranian nuclear program in check and under close surveillance.”
In a phone call, President Emmanuel Macron of France also urged Mr. Trump not to scrap the deal. Mr. Macron “reaffirmed France’s determination to see the agreement strictly enforced and the importance for all of its signatories to abide by it,” his office said in a statement.
Privately, some White House officials complained about the phone call with Mr. Macron, which they said could have provoked Mr. Trump. Others said the diplomatic meeting in Brussels was similarly ill-conceived, and they expressed frustration that the legislative efforts in Congress were not progressing quickly enough.