But Mr. Pompeo did not say how Washington might react if Iran’s inventory of nuclear material increased to the point that Iran got within striking distance of building a bomb.
Mr. Rouhani, meanwhile, is gradually raising the temperature, testing whether he can peel European governments away from the United States in the conflict over the 2015 accord. In his speech in May, he set a series of 60-day deadlines, threatening to discard nuclear restrictions, one by one, if Britain, France and Germany did not break the sanctions that the United States has imposed unilaterally. The first step, Mr. Rouhani said, would be a quadrupling of uranium production.
The second step, come July, he said, would be increasing the level of enrichment, taking the country closer to bomb-grade uranium. But Mr. Rouhani did not say how much the enrichment level would increase.
Mr. Amano’s statement on Monday came as Germany’s foreign minister, Heiko Maas, was visiting Iran, trying to succeed in the delicate work of separating Germany from American policy while not threatening Germany’s alliance with the United States.
“The situation in the region here is highly explosive and extremely serious,” he said. “A dangerous escalation of existing tensions can also lead to a military escalation.”
But as Iran walks back from its nuclear commitments, American diplomats say, it will be increasingly difficult for Germany and other Western European nations to do business with Tehran. For more than a year, Europe and Iran have discussed creating what essentially amounts to a barter system, one that would allow Europe to obtain Iranian oil in return for European goods without conducting transactions in dollars, which Washington has blocked.
Iran’s foreign minister, Mohammad Javad Zarif, has complained for months that the system has not been put into place, and, in private, Europeans say they have doubts it ever will be.
“We want to fulfill our obligations” under the 2015 agreement, Mr. Maas said during a joint news conference with Mr. Zarif. But he said that “we cannot work miracles.”