Donald Trump’s voice in foreign affairs is one that slips between brash arrogance and oily smugness. He touts supremacy from behind thinly concealed contempt. In withdrawing America from the Iran nuclear agreement, officially known as the Joint Comprehensive Plan of Action (JCPOA), Mr Trump risks pushing Iran out into the cold, triggering a nuclear arms race in the Middle East and handing power to the hardliners in Tehran. In place of the UN-approved deal is little more than Mr Trump’s bombastic promises of greater American independence and fewer unnecessary constraints.

Mr Trump all but declared war on Iran in a speech largely estranged from fact. Contrary to his claims, Iran has abided by the agreement, as UN weapons inspectors attest. Tehran is not on the “cusp of acquiring the world’s most dangerous weapons”. In fact the deal allows Iran to continue to enrich uranium – but it is neither allowed nor technically able to use this process to produce weapons-grade uranium. Under the agreement, Iran cannot reprocess plutonium either, an alternative path to a nuclear explosive. Mr Trump’s invective should surprise no one; he relies on assertions that reinforce prejudices but have no basis in truth.

The premise of the JCPOA was to allow Iran to benefit from the global economy in exchange for denuclearisation. It is now incumbent on the US to, in Mr Trump’s words, find a “lasting solution to the Iranian nuclear threat”. Yet there is no plan forthcoming from the White House. The absence of American leadership in the world will mean that the Europeans – principally the main powers of the UK, Germany and France – will have to work reluctantly with Russia and China to uphold the agreement. This will require protection for firms and banks engaged in trade and financial transactions with Iran. Without Washington’s support this may mean resorting to non-dollar deals to evade US sanctions. Like his rejection of the Paris climate deal, Mr Trump opposed the Iranian nuclear deal not because he understood the details and consequences of a complex agreement’s terms but because he wanted, scandalously, to signal that former US president Barack Obama did not necessarily have US interests at heart when he negotiated the agreement. When international agreements are not insulated from partisanship by constitutional principle, then deals are likely to be stop-gap solutions. North Korea will understand this lesson only too well.

The US is the author of Iran’s success. Its disastrous invasion of Iraq saw Iranian influence grow along a Shia crescent in the northern Middle East. Tehran’s proxies prop up the murderous dictatorship of Bashar al-Assad in Syria and have emerged as powerful political blocks in Lebanon and Iraq. The anti-Iranian outbursts by Mr Trump and his team create a narrative in which war with Tehran is the only viable policy.

Goading Iran’s hardliners to restart weapons programmes is an extremely high-risk strategy likely to trigger to a military confrontation between the US and Iran and probably the Syrian regime. The problem is that such a conflict would most likely also involve Russia and Israel, the latter an undeclared nuclear power and Iran’s most vocal critic. Meanwhile Saudi Arabia is pushing for the right to either enrich or reprocess nuclear material. If it is allowed to then no doubt the United Arab Emirates, with its history of turning a blind eye to illicit nuclear weapons programmes, would want to do the same. Mr Trump is opening a Pandora’s box in the Middle East. The world needs to convince him to close it.