US Secretary of State Rex Tillerson on April 19 described the nuclear deal with Iran as a failure, saying it only delays Tehran’s goal of becoming a nuclear state.

The deal agreed with the major powers "fails to achieve the objective of a non-nuclear Iran," Tillerson said at a Washington news conference, adding: "[Iran’s] nuclear ambitions are a threat to the world's peace and security... An unchecked Iran has the potential to travel the same path as North Korea and take the world along with it."

Also hitting out at what he perceived as Iran’s "alarming ongoing provocations" in the Middle East, Tillerson underlined how the 90-day review of the nuclear deal by the Trump administration, which was announced on April 18, would not only look at Iran’s compliance with the deal, but at whether Tehran's behaviour in the region continued to undermine American interests.

Iran has repeatedly said it has never sought to develop nuclear weapons, but in return for the easing of economic sanctions the Iranians in November 2015 agreed to scale down their nuclear fuel development activities.

In further harsh comments, Tillerson said the agreement would simply "buy off a power that has nuclear ambitions" for a short while before leaving the problem to future generations to resolve. "The Trump administration has no intention of passing the buck to a future administration on Iran," he said.

On April 18, however, in a letter to Congress, Tillerson did concede that Iran was currently complying with the nuclear deal.

Iranian Supreme Leader Ayatollah Khamenei has previously warned that Tehran will retaliate if the Washington breaches the multilateral agreement.