Iran said on Monday that it had started using a new set of advanced centrifuges, bringing the country a step closer to being able to produce enough nuclear material for a bomb.
It is the latest move made by Iran to exceed the limitations of the nuclear agreement it signed in 2015, and it was done in retaliation for President Trump’s withdrawing from that deal and imposing new economic sanctions.
The Iranian government reiterated that it was prepared to reverse its buildup if the European powers that signed the agreement found a way to ease the impact of the American sanctions.
Tehran has pursued a calibrated campaign of steps beyond the boundaries of the 2015 deal, steadily ratcheting up pressure on the Europeans. But if European commitments “are fully implemented, we will come close to what we had in the nuclear deal, too,” Ali Rabiei, a government spokesman, said at a news conference in Tehran, according to the semiofficial Fars News Agency.
“Our final goal is full implementation of the nuclear deal,” he said, adding that Iran’s moves “are aimed at bringing the other side back to compliance.”
The announcement came as Iran celebrated the 40th anniversary of the seizure of the United States Embassy in Tehran, when 52 Americans were taken hostage.
In Washington, the Trump administration marked the anniversary with new sanctions on Iranian leaders. The Treasury Department action targeted the general staff of Iran’s armed forces and nine associates of Ayatollah Ali Khamenei, the country’s supreme leader. Among them were the ayatollah’s chief of staff, one of his sons and the head of Iran’s judiciary.
“This action further constricts the supreme leader’s ability to execute his agenda of terror and oppression,” Treasury Secretary Steven T. Mnuchin said in a statement.
The 2015 nuclear agreement limited Iran, for 10 years, to using about 5,000 older centrifuges at its main nuclear development facility. But in April, it announced plans to use newer, more efficient centrifuges not been allowed under the agreement. In the summer it began to install and activate them.
On Monday, Ali Akbar Salehi, the chief of the Atomic Energy Organization of Iran, told state news media that 30 of the more advanced centrifuges had been put into use, bringing the total to 60. He said that Iran was also making plans to install more advanced centrifuges in the future.
The centrifuges are used to separate the rare, highly radioactive isotope, uranium 235, from the less radioactive type, uranium 238. Increasing the proportion of uranium 235 is known as enrichment.
Under the nuclear deal, Iran gave up the majority of its enriched uranium stockpile, agreeing to keep no more than 660 pounds for 15 years. It also agreed to limit its enrichment to less than 4 percent uranium 235.
In recent months, Iran has gone beyond both the total amount and the level of enrichment that were allowed under the agreement.
Its supplies are still far short of the level of enrichment needed to make a nuclear bomb, however. Iran insists that it has no intention of building such a weapon, but Israeli, American and Saudi officials have long disputed that claim.
Besides imposing new sanctions on Iranian leaders on Monday, the Trump administration also raised a $5 million reward to $20 million for information leading to the recovery of Robert A. Levinson, an American who disappeared in Iran in 2007. Mr. Levinson, a former F.B.I. agent who worked as a private investigator and part-time consultant for the C.I.A., vanished while trying to recruit an intelligence source for the C.I.A. He has not been seen in nearly a decade.
David E. Sanger and Peter Baker contributed reporting.