Iran brought this new isolation upon itself

On the day following the deal five years ago to restrict Iran’s nuclear weapons programme, we said caution was advisable, even if the agreement appeared to be a pragmatic solution to a deepening diplomatic conundrum. The so-called Joint Comprehensive Plan of Action (JCPOA) represented a landmark accord between America and the country that had been its foremost enemy since the Islamic revolution of 1979. The deal was hailed by its proponents in Geneva as a triumph of enlightened diplomacy that had made the world a safer place.

As of last night it has been partially torn up, after Donald Trump fulfilled his election campaign pledge to withdraw US support for what he has called with characteristic hyperbole “the worst deal ever”. The upshot is the reimposition of high-level American sanctions on Tehran aimed at hampering its international oil trade. Theoretically, the other signatories to the deal – the UK, France, Germany, Russia and China – could keep it going.

In recent weeks, a steady procession of EU leaders and politicians, from Emmanuel Macron and Angela Merkel to Boris Johnson, the Foreign Secretary, travelled to Washington to try to persuade the President to stay on board by renewing the 120-day waiver, but to no avail. Mr Trump has left open the prospect of a revived accord if the other signatories succeed in getting a better deal. But that would require Iran’s co-operation, which seems unlikely. Without America’s backing, Tehran may now take the view that the multilateral accord has expired, and act accordingly.

The collapse of the JCPOA is regrettable because it signifies a breach in a common front against Iran. But Mr Trump’s objection is not only with the nuclear programme; it is also with Iran’s wider destabilising actvities. The deal has failed in its principal purpose, which was to enhance the security of Israel and Sunni Arab powers and reduce the risk of a Middle East arms race.

In the five years since Geneva, Iran has interfered in the Syrian conflict to prop up Bashar al-assad, turned Iraq into a satrap of Tehran and used its Hizbollah allies to take over Lebanon by proxy. No one knows for certain that it has even stopped its secret nuclear programme, since the regime denies ever having embarked on one, despite all the evidence to the contrary. The solution to Iran’s renewed isolation is in its own hands: stop threatening other countries in the region.