Economist - FRANCE’s president, Emmanuel Macron, ended a three-day state visit to Washington this week glumly predicting that for “domestic reasons” Donald Trump will pull out of the Iran nuclear deal brokered by world powers in 2015, as soon as next month. What happens if Mr Trump does so?

In theory it is not in Mr Trump’s power simply to end the deal, which was agreed by his predecessor, Barack Obama. It is a political agreement between Iran and six world powers: Britain, China, France, Germany, Russia and the United States. Formally the Joint Comprehensive Plan of Action (JCPOA), the agreement lifted nuclear-related international and American sanctions on Iran in exchange for physical, verifiable curbs on Iran’s ability to produce or stockpile fissile material for nuclear weapons for at least 10 to 15 years. European governments, plus China and Russia, have made clear that they regard the JCPOA as binding, given that Iran is deemed by international inspectors to be in compliance with its terms. In practice, the re-imposition of swingeing American sanctions—especially secondary sanctions that would hit European banks and businesses trading with Iran—could kill the deal or turn it into the diplomatic equivalent of a zombie.

Mr Trump scorns the deal as the “worst” ever and has long promised to terminate it. He has plenty of chances to disavow the deal, thanks to deadlines imposed by Congress, which require America’s president to review every few months whether America should continue to suspend its sanctions, or re-impose them. The next deadline falls on May 12th and Mr Trump is keeping the world guessing. At a joint press conference with Mr Macron on April 24th Mr Trump seemed to praise his French visitor’s suggestion of a new multinational agreement to constrain Iranian mischief-making that would build on and enlarge the scope of the Obama-era pact. Yet Mr Trump also continued to denounce that original pact as “insane”.

Uncertainties abound. The May 12th deadline is not as final as it seems. American sanctions up for review then mostly concern Iranian oil exports and other trade denominated in dollars, and work by targeting Iran’s banks and those who deal with them. Arguably, a more important deadline falls in mid-July when Mr Trump must review sanctions targeting a broad range of sectors from shipping to aviation. Iranian officials have threatened to abandon the JCPOA if America “betrays” its terms. In a worst case Iranian hardliners could resume work on nuclear weapons, defying Mr Trump’s threats of “big problems” if they choose that course. Iran could stick with the deal and seek to expand trade with non-American partners—though major international firms are likely to fear being shut out of American markets. In a best case, Mr Trump could work with Europeans on side agreements that seek to limit Iranian ballistic-missile programmes, to curb Iranian meddling in the Middle East and to make permanent constraints on Iran’s nuclear-weapons development. But without the JCPOA as a foundation, such side deals would stand on dangerously shaky ground.