"They do bad, bad things," US President Donald Trump said of Iran in his February 5 State of the Union address to Congress.

To which Iranian Foreign Minister Mohammad Javad Zarif responded on Twitter: "U.S. hostility has led it to support dictators, butchers & extremists, who've only brought ruin to our region."

The clash underlined how not one jot of progress has been made in bringing Tehran and Washington to the table for talks since in May last year Trump unilaterally pulled the US out of the multilateral nuclear deal with six major powers and embarked on the heaviest sanctions campaign mounted against Iran since the Islamic Revolution almost exactly 40 years ago.

Trump added in his speech that Iran’s rulers were running a “radical regime". He vowed that Iran would never acquire nuclear weapons.

However, in making such declarations Trump is even out of tune with his own intelligence chiefs. They lately informed Congress that their analysis shows Iran does not seem to have moved into activities with which it would progress towards developing a nuclear bomb.

The purpose of the nuclear deal is to ensure Iran complies with measures that prevent it from doing so in return for protection from crippling sanctions. The UN’s atomic watchdog has repeatedly found that Tehran has remained in compliance with those measures. Its latest endorsement came last month. Nuclear deal signatories France, Germany, the UK, Russia and China are content with its assessment.

The US president also said in his address: “My administration has acted decisively to confront the world's leading state sponsor of terror: the radical regime in Iran.”

Iran denies that it supports terrorist groups. It is clear that it backs certain favoured militant groups in countries including Lebanon, Syria, Iraq and Yemen but the Iranians maintain that neighbours who are US allies also do so and that Iran, as a country located in the Middle East, has every right to defend its interests in the region.