But Mohammad Javad Zarif said he hoped Europe would keep the agreement alive.
US President Donald Trump - a stern critic of the deal - will announce next month whether he believes Iran has adhered to its terms.
If he says it has failed to do so, US Congress will begin the process of reimposing sanctions on Iran.
Mr Trump said the agreement was an "embarrassment" in a speech to the United Nations this month.
France, Germany and the UK - which along with Russia and China signed the deal - have recently defended it.
In an interview with two British newspapers, Mr Zarif said that if the deal collapsed, Iran would no longer have to follow its limitations on uranium enrichment, centrifuge numbers and the production of plutonium. But he insisted Iran would only use nuclear technology for peaceful purposes.
"You either live by it [the deal] or you set it aside," Mr Zarif told the Financial Times and the Guardian. "You cannot be half pregnant."
"My assumption and guess is that he [Trump] will not certify and then will allow Congress to take the decision," Mr Zarif said during the interview at the Iranian UN mission's residence in New York.
"The deal allowed Iran to continue its research and development. So we have improved our technological base. If we decide to walk away from the deal we would be walking away with better technology."
He said of Mr Trump: "I think he has made a policy of being unpredictable, and now he's turning that into being unreliable as well. He has violated the letter, spirit, everything of the deal."
Mr Zarif said Iran's options "will depend on how the rest of the international community deal with the United States"."If Europe and Japan and Russia and China decided to go along with the US, then I think that will be the end of the deal," he said. "Europe should lead."European Union officials have said they could act to legally protect European investors in Iran if the US reimposes sanctions.
But, in line with the US, they have also criticised Iran over its non-nuclear activities in the region.
Iran nuclear deal: Tehran expects US to ditch agreement, says FM
01 October 2017
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Iran's foreign minister has said he assumes that the US will abandon the international deal restricting his country's nuclear activities.
