Iran’s foreign minister has said he expects US President Donald Trump will not uphold a historic nuclear agreement next month, and called on Europeans to step in to protect the deal. Javad Zarif also maintained in an interview with the Financial Times and the Guardian that if the deal collapses, Iran would no longer have to abide by its limitations — which include curbs on uranium enrichment, centrifuge numbers and the production of plutonium. “You either live by it, or you set it aside,” Mr Zarif said of the agreement, which he depicted as a done deal, not to be renegotiated. “You cannot be half pregnant.”

If Mr Trump does not “recertify” the agreement at 90 day intervals — the next of which is due on October 16 — Congress has 60 days to decide whether to impose new sanctions. Such a step by Capitol Hill could lead to the implosion of the deal — which is cosigned by other world powers and was passed into international law by the UN Security Council. Mr Trump called the agreement an “embarrassment” in a speech to the UN this month.

“My assumption and guess is that he will not certify and then will allow Congress to take the decision,” Mr Zarif said 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,” he added. “If we decide to walk away from the deal we would be walking away with better technology.” Mr Zarif, who insisted Iran would only use nuclear technology for peaceful purposes, said the country’s options “will depend on how the rest of the international community deal with the United States”.

France, Germany and the UK — which together with Russia and China make up the deal’s signatories — have rallied to its defence after they began to realise that Mr Trump might seek to undermine it to a breaking point.  “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,” Mr Zarif. “Europe should lead.”

European diplomats argue that if the deal is kept alive it would also offer evidence that Washington can keep its word as it seeks talks with North Korea over Pyongyang’s own nuclear programme.  But they say privately that the US — which acknowledges Iran is in “tactical” compliance with the deal — is set on hardening its line on Tehran.

“I think he has made a policy of being unpredictable, and now he’s turning that into being unreliable as well,” Mr Zarif said of Mr Trump. “He has violated the letter, spirit, everything of the deal,” he added, countering claims Iran is in default of the “spirit” of the deal over its regional activities. EU officials have said they could move to legally protect European investors in Iran should the US reimpose sanctions. But they have also stepped up criticism of Tehran over its non-nuclear activities in the region. The UK in particular has discussed with Mr Trump making the inspection regime for Iran’s nuclear programme more effective and has expressed concern about so-called sunset clauses, which are set to phase out some restrictions on Iran’s activities from 2025.