Several US media outlets on October 6  reported that Donald Trump will next week refuse to certify Iranian compliance with the nuclear deal.

The American president has accused Iran of not living up to the “spirit of the agreement”. At a meeting of military leaders, Trump reportedly warned cryptically that those present were witnessing “the calm before the storm”. When asked by reporters what he was implying, the former reality TV host said: “You’ll find out.”

The media outlets cited sources as saying that even though Iran is widely held to be complying with the letter of the landmark agreement that eases sanctions against the country in return for a drastic scaling down of its nuclear development programme, Trump will not certify the 2015 deal with six major powers on the grounds it does not serve US security interests.

That would trigger a period of 60 days in which it would be up to Congress whether to reimpose sanctions. A decision to do so could mean the collapse of the deal and a return to a tense standoff in the Middle East over Iran’s progress to a nuclear weapon. Europe, China and Russia, however, might attempt to keep the deal going without US participation.

“The Iranian regime supports terrorism and exports violence and chaos across the Middle East,” Trump said at a White House meeting of US military leaders. “That is why we must put an end to Iran’s continued aggression and nuclear ambitions,” he added. “You will be hearing about Iran very shortly.”

Trump’s own most senior military leaders, including defence secretary, James Mattis, have said that staying with the deal does appear to currently be in US national security interests.