In the interview, Mr. Zarif accused the West of trying to sabotage a heavy-water reactor under construction near Arak by altering components of its cooling system, a step he said could have led to an “environmental catastrophe.” But he did not directly blame the United States.

“You know about cyberattacks,” Mr. Zarif said, referring to the American- and Israeli-led operation called Olympic Games that blew up roughly one thousand centrifuges at the Natanz nuclear enrichment plant until it was discovered in 2010. He said a foreign power had tried “to create malfunctions in equipment” purchased for the Arak plant from outside Iran “so that for instance instead of cooling the facility they would have increased the heat in the facility, had we not detected it” in time.

Mr. Zarif offered no evidence, and when pressed, he said his own briefings on the subject have been sketchy. Arak has been a known target of Western intelligence because it has the potential to produce weapons-usable plutonium. He said Iranian engineers found what he contended was sabotage before it could create “huge problems.”

The core measure of whether Mr. Zarif’s proposal will gain traction focuses on what nuclear experts call “breakout capacity,” the speed at which Iran could produce the fuel for a single nuclear weapon. The American position has been that only by dismantling a large proportion of Iran’s centrifuges can the United States and its European allies extend that time to a year or more.

Mr. Zarif combined his proposal of a freeze with an offer to take the nuclear fuel produced by its 9,000 or so working centrifuges and convert it to an oxide form, a way station to being made into nuclear fuel rods. He said that Iran would guarantee, during the agreement, not to build the facility needed to convert the oxide back into a gas, the step that would have to precede any effort to enrich it to 90 percent purity, which is what is generally considered bomb-grade.

He clearly signaled that he had some room to negotiate on how long the freeze would last because Iran has an agreement with Russia to provide fuel for its Bushehr nuclear plant for the next seven years. “We want to produce only what we need,” he said. “Since our reactor doesn’t need fuel for another seven years we don’t have to kill ourselves for it. We have time.”

American officials say that argument is specious; Russia must license the fuel for its reactor and does not want to give up the business. They doubt Iran could safely make the fuel for that reactor.