The Europeans reiterated that they opposed Mr. Trump’s withdrawal from the deal and were not joining his campaign of “maximum pressure” to cripple Iran economically. “Our hope is to bring Iran back into full compliance,” they said.

The three nations “took the right step,” the State Department said in a statement, adding that “nations must unite behind this effort to hold the Iranian regime accountable for its continued destabilizing actions.”

There was no immediate reaction from Tehran.

The 2015 agreement restricted how many centrifuges Iran could use to enrich uranium — increasing the percentage of U-235, the rare isotope crucial to its use in nuclear fission — how highly it could enrich the metal, and how much uranium it could stockpile.

It has taken a series of steps beyond those limits, trying in vain to pressure the Europeans to make good on a commitment to ease the economic pain of American sanctions.

Earlier this month, in response to the Suleimani killing, Iran said it would no longer abide by any restrictions in its uranium enrichment, but without specifying what it would actually do, which was taken by the Europeans as a useful ambiguity.