The odds on the Trump administration attempting to kill the Iran nuclear deal substantially shortened on March 13 with the firing-by-tweet of US Secretary of State Rex Tillerson and his replacement with CIA chief and foreign policy hawk Mike Pompeo.

Tillerson has in the past year openly disagreed with US President Donald Trump's desire to see the accord—formally known as the Joint Comprehensive Plan for Action (JCPOA)—scrapped but in contrast, in November 2016, Pompeo even went as far as to post on his then personal Twitter account: “I look forward to rolling back this disastrous deal with the world’s largest state sponsor of terrorism.”

Tillerson was engaged with France, Germany and the UK in finding a way to adjust the JCPOA to Trump's satisfaction following his White House announcement on January 12 that he was providing the multilateral agreement's signatories with a “last chance” to fix the deal's “terrible flaws” and giving them 120 days to do so.

But the wide distance that remained between the two men on the issue was shown by remarks Trump made to reporters outside the White House on March 13 after the dismissal of Tillerson had been announced. Trump said his overall differences with Tillerson came down to personal "chemistry", and added: "We got along actually quite well, but we disagreed on things. When you look at the Iran deal [for instance], I think it's terrible. I guess he thought it was OK. I wanted to either break it or do something and he felt a little bit differently, so we were not really thinking the same.”

Also on March 13, Iran’s foreign minister, Mohammad Javad Zarif, tweeted: “Mr Trump has made habit of being unpredictable and thus unreliable for anybody to engage with. Nobody will be interested in reaching any agreement with the White House if US signature only good for 4-8 yrs.”

France, Germany and the UK have been under huge pressure from the US and Persian Gulf adversaries of Iran to rip up the JCPOA, or at least add supplements covering the Iranian ballistic missile development programme, even though Tehran protests it is not designing missiles to carry nuclear payloads.

Like Trump, Pompeo, who in his year leading the CIA approved new powers to target leaders of Iran’s Islamic Revolutionary Guard Corps (IRGC) through intelligence operations, is unhappy that the JCPOA provisions barring Iran from moving towards the development of a nuclear weapon—in return for the dropping of major oil export, banking and other sanctions against the Iranians—are drawn up to expire in 2025 under “sunset clauses”.

On March 11, Pompeo told CBS's Face the Nation: “My critique of the Obama administration’s JCPOA commitment was that they left the Iranians with a breakout capacity. They had a short time frame that these would... these restrictions would remain in place.”

Although Iranians typically point out that the Sunni Muslim al Qaeda terrorist group has always regarded Shiite Muslim Iran as an arch-enemy, Pompeo is also on record as claiming that this is not the way things work. Last September, in an interview with Bloomberg, he remarked: “Iran has always made a devil’s bargain with al Qaeda to protect them in many ways. And that protection was often contingent on a deal which said if we protect you, you won’t attack us here in Tehran.”

“Pompeo has a sort of hard-line approach on foreign policy that’s quite black and white, and that’s also how Trump sees the world,” Ilan Goldenberg, a senior fellow at the Center for a New American Security who worked at the State Department under then-Secretary John Kerry, told Bloomberg in an interview last December. “This is where Pompeo has really been able to endear himself to Trump.”