Iran’s adherence to its commitments within the accord prompted heated arguments inside the administration that continued on Monday before Mr. Trump finally agreed to certify that Iran was in compliance with its obligations.
The sanctions announced the next day cited continued Iranian development and testing of missiles, the country’s support of President Bashar al-Assad of Syria and its escalating cyberactivity, including the theft of software.
Mr. Zarif said Iran would “reciprocate,” but made the promise in a weary way, saying that Iran’s sanctions on Americans would be no more effective than American efforts to block travel or financial transactions with 18 Iranian individuals and entities.
But the bigger casualty, Mr. Zarif acknowledged in a 90-minute conversation with an invited group of journalists, was the prospect that the deal would mark a shift in more than three decades of antagonism between Washington and Tehran that dated to the Islamic Revolution and the overthrow of the Shah.
Two years ago there was talk of whether, with the nuclear dispute behind them, the United States and Iran might cooperate against the Islamic State and strike a deal over Syria. Traditional Sunni allies of the United States like Saudi Arabia wondered if Washington was about to pivot toward Iran, which has a predominantly Shiite population, for the first time since the Shah’s fall.
Indeed, the deal was seen as a major gamble by the Obama administration. Over time, many officials thought, the two countries would use it as a foundation for building a larger relationship.
Today that foundation is crumbling. Administration officials say the debate over whether to ultimately scrap the accord continues, though they acknowledge that doing that would free Iran to resume enrichment of uranium and reprocessing of plutonium, the exact activities the deal sharply limits.
On Sunday, Iran disclosed that it had been holding Xiyue Wang, an American who is a Princeton University doctoral candidate in history, for nearly a year and has sentenced him to 10 years in prison on spying charges. The disclosure shocked Mr. Wang’s colleagues at Princeton, who described Iran’s action as a colossal error. The incarceration of Mr. Wang, 37, also threatened to chill academic exchanges between Iran and the United States.
The reception Mr. Zarif receives now in Washington could not be more different than it was 24 months ago. He and Mr. Kerry developed a close rapport, even if it was often punctuated by shouting matches. But Mr. Zarif said he had never spoken with Mr. Kerry’s successor, Rex W. Tillerson.
“I haven’t asked for a meeting, and I don’t think I will,” he said.
If new discussions do begin with the United States, he said, they would start on the question of whether it is violating key paragraphs of the nuclear deal that prohibit the United States or other signers from blocking Iran from enjoying the benefits of renewed economic interaction with the rest of the world.
Those benefits have been slow to come to Iran. At one point Mr. Kerry met with European bankers to encourage them to reopen their dealings with Tehran, fearing that a backlash against the deal would occur if the West did not seem to be living up to its side of the accord.
Whether the Trump administration is actively violating the agreement by reimposing sanctions under a different rationale is a debatable legal point, though a number of American experts said that Mr. Zarif had a plausible case. The agreement has a mechanism in place to resolve both small and large disputes, which Mr. Zarif suggested Iran was about to become the first to invoke.
The accord specifies that the United States, and other partners in what is formally known as the Joint Comprehensive Plan of Action, “will refrain from any policy specifically intended to directly and adversely affect the normalization of trade and economic relations with Iran inconsistent with their commitments not to undermine the successful implementation” of the agreement.
The Trump administration insists — as the Obama administration did — that such wording allows for sanctions to counter human rights violations, weapons proliferation or support of terrorism. In fact, Mr. Obama imposed some sanctions the same day the accord went into effect in 2016.
The sanctions announced on Tuesday are similar to those Mr. Obama invoked. But the intent may be different. Last week Sarah Huckabee Sanders, the deputy White House press secretary, told reporters that at the Group of 20 meeting in Hamburg, Germany, Mr. Trump actively argued for isolating Iran, telling “more than a dozen foreign leaders” that they needed to “strip terrorists of their funding, territory and ideological support, and stop doing business with nations that sponsor terrorism, especially Iran.”
Mr. Zarif said he was philosophical about the change in tone. He had allowed for that during the negotiations, he said, noting that the document “was negotiated and drafted based on mutual distrust.”
“You will see that mistrust every sentence,” he added.
Mr. Zarif dodged questions about Iran’s activities in the Middle East, saying he did not know how many Iranian or Shiite militias were in Syria, and he declined to criticize Mr. Assad. He questioned whether Mr. Assad’s government was responsible for the chemical attack that led to American retaliation in April.
“Why would he do something” like the chemical weapons attack, Mr. Zarif asked about Mr. Assad, “the day after the president indicates removing Assad is not an American priority?”
Similarly, Mr. Zarif was defensive about Iran’s continued missile testing, saying it needed accurate missiles as a deterrent against the Sunni Arab states that the United States arms with its “beautiful American military equipment” sold to the region.