Mr. Rouhani said Iran was reactivating Fordow, which is adjacent to an Iranian military base, precisely because it was considered such a hard military target. Its renewal as a nuclear production site, he suggested, could be easily reversed — part of the carefully calibrated strategy Iran is pursuing to pressure the United States and its allies just as the American-led sanctions on Iran’s oil shipments are intended to pressure Tehran.

“We know how sensitive they are to the Fordow facility,” Mr. Rouhani told the country in a speech about why Iran would no longer abide by an agreement that Mr. Trump has abandoned. But he made clear that he regarded Fordow as a mere bargaining chip, saying that when the United States begins “living up to their commitments” to suspend sanctions while Iran was in compliance with the deal, “then we will stop feeding gas to the centrifuges.”

The State Department criticized Mr. Rouhani’s actions on Tuesday. “Iran has no credible reason to expand its uranium enrichment program, at the Fordow facility or elsewhere,” it said in a statement, “other than a clear attempt at nuclear extortion that will only deepen its political and economic isolation.”

It was the third time in six months that Mr. Rouhani had announced a careful series of escalations of Iran’s nuclear capacity. On Monday Iran said it was already producing enriched uranium at an ever-faster pace at its primary nuclear enrichment center at Natanz. In recent weeks it has also discussed rebuilding a plutonium reactor that was disabled under the agreement before it ever went into operation. That process is likely to take years.

None of these steps immediately gets Iran the makings of a bomb. But taken together, they create the condition that the three-year-long negotiating process was intended to stop, at least for a while: Iran’s ability to develop the material for a bomb in a year. President Trump’s complaint with the Iran accord was that key restrictions expired by 2030, but the net result of the recent announcements is that those restrictions are largely being thrown out now.