It was unclear whether the assembly center would actually begin to produce new centrifuges.
Under the 2015 nuclear deal, Iran stopped enriching uranium to the 20 percent level that would allow for rapid development of a nuclear weapon and agreed to a limit of under 5 percent. It will adhere to that limit, Iran’s supreme leader, Ayatollah Ali Khamenei, said in a speech on Monday.
It was also uncertain whether the opening of the centrifuge plant would have any significant impact on Iran’s nuclear program, which continues to be closely monitored by the International Atomic Energy Agency.
When Tehran agreed in 2015 to roll back its nuclear program in exchange for the lifting of international and United States sanctions, European companies rushed to enter the Iranian market. European governments have been working to keep the deal alive and protect those investments after President Trump dismayed many on the Continent by withdrawing and reimposing banking sanctions.
However, the American sanctions would still be a major problem, particularly for multinational companies, and several European firms have already announced plans to pull out of Iran. On Monday, the French group PSA, the maker of Peugeot and Citroën cars, which produces 440,000 vehicles a year in Iran, started closing its joint ventures with local auto manufacturers, though PSA said it would seek a waiver from the United States to maintain that production level.