Iran Steps Further From Nuclear Deal With Move on Centrifuges

The agreement was signed in 2015 by Iran and the United States, along with China, France, Russia, Britain, Germany and the European Union. Iran agreed to reduce the size of its nuclear program in exchange for relief from sanctions.

Mr. Trump, in withdrawing from the pact, reimposed old sanctions, and later added new ones. Iran has argued that it cannot abide by the deal as long as the sanctions are crippling its economy, while at the same time saying it would adhere to the agreement if the European partners to the nuclear agreement could lessen their effect.

The European signatories, which still support the deal, have sought to find ways to address the Iranian concerns but have been unable to come up with alternatives that satisfy Tehran without running afoul of the United States sanctions.

Maja Kocijancic, a spokeswoman for the European Commission, the European Union’s executive arm, said the union was “concerned” about the announcement, urging to Iran to reverse earlier breaches of the nuclear deal and refrain from any further moves that would undermine it.

Dmitri S. Peskov, the Kremlin spokesman, said that Russia would like to see the nuclear deal remain in force, but he also expressed sympathy for Iran, citing the “unprecedented and illegitimate sanctions” against it.

Russia’s state-run nuclear company, Rosatom, was recently granted a waiver to continue work at the Fordow site, The Associated Press reported, but Moscow does not expect the developments on Tuesday to affect its role there.

The Fordow fuel enrichment plant was discovered in April 2008, and unlike the facility at Natanz, it is too small to produce an effective amount of nuclear fuel for civilian purposes, leading the West to conclude that its purpose was to help create a nuclear weapon. Iran has consistently denied that it is seeking to build a bomb.