WASHINGTON — If Congress were to reject the world powers’ nuclear deal with Iran, US leadership and the stability of the US dollar would be threatened, Secretary of State John Kerry warned Tuesday. Speaking to an audience in New York City at an open discussion on the merits of the agreement, Kerry also emphasized that Tehran had shown restraint in its pursuit of an atomic weapon even before talks began toward the deal, which puts curbs on Iran’s nuclear program in exchange for sanctions relief.

Kerry lashed out at critics of the deal, reached between Iran and the P5+1 nations — the US, Britain, France, Russia, China and Germany — last month, who say that the United States should reject the agreement, reapply sanctions, and return to the bargaining table to hammer out a more stringent deal. Prime Minister Benjamin Netanyahu has been the most strident critic of the deal outside the US.

The secretary of state asked audience members to consider a situation in which the US reimposed sanctions, and then “is going to start sanctioning our allies and their businesses after we walk away from the deal? Are you kidding me?” He warned, “That is a recipe very quickly for the American dollar to cease to be the reserve currency of the world – that is already bubbling out there.”

Later in his talk, Kerry indicated that the Department of the Treasury has been preparing a report that would delineate the potential damage to the US economy should Congress reject the deal. “The notion that we can just sort of diss the deal and unilaterally walk away, as Congress wants to do, will have a profound negative impact on people’s sense of American leadership and reliability,” he cautioned.

Congress is halfway through a 60-day review period of the agreement that is expected to end with a vote on a resolution of disapproval. The White House is trying to enlist sufficient support for the deal to sustain a presidential veto of the vote.

Kerry repeatedly emphasized that the deal was a “good” one that “gets the job done.”

He acknowledged that America’s “judgment is that clearly there was a period in which Iran was chasing a nuclear weapon,” but seemed to indicate that that pursuit had ceased before Iran came to the negotiating table in 2013, a statement that is in line with American intelligence assessments.

“There has been a fight within Iran, and it continues in some quarters, about where they should go with respect to their nuclear program,” Kerry noted. “They have not pursued a weapon, to our best judgment and to the judgment of our allies, since that period of time,” he continued, referring to the previous decade.

“The Ayatollah Khamenei has issued a fatwa that nobody should pursue a nuclear weapon,” he argued. “And we’ve essentially said to them, ‘Let’s take that fatwa and make it into an agreement.’

Nonetheless, he added, “the [Iranian Revolutionary Guard Corps] still wants one, and they are opposed to the agreement, but the government has adopted an agreement in which they are forbidden forever from producing a nuclear bomb.

“When I hear a congressman or senator say we should get a better deal — that is not going to happen,” Kerry emphasized. “There is not a better deal to be gotten.” He said that in both 2003 and 2008, president George W. Bush “tried to get a better deal,” but that following both of those attempts, Iran expanded its enrichment capacity and stockpiled the resulting fissile material, which can be used to build a bomb.

Kerry reiterated his claim that, throughout that time, “they could rapidly break out if they chose too, but they didn’t.

“They are a nuclear threshold nation today,” he added. “They became that and they became that when we had a policy of no enrichment.”

Still, he argued, “when they had enough fissile material for 10 to 12 bombs, we don’t believe they went ahead and tried to make that bomb.”

Kerry also offered a limited step-back from accusations leveled by administration representatives to the effect that those who oppose the deal are seeking to drag America into war.

“Its better that we don’t go down that path but argue this on the merits, because I think the merits are strong, and the president does too,” he said in response to an audience members’ question about the increasingly aggressive rhetoric employed by both critics and proponents of the deal.