As John Kerry, US secretary of state, works to build a coalition to defeat Islamic State of Iraq and the Levant, known as Isis, the piratical jihadi group presiding mainly over desert straddling Iraq and Syria, he faces demands from Syria, Russia and Tehran itself to include Iran. But if Tehran desires to join others to defeat the bogus caliphate, it must first reverse policies in Iraq and Syria that keep Isis in business.

It is true that Tehran plays outsize roles in both Iraq and Syria. In the former, having disposed of Prime Minister Nouri al-Maliki, who with his divisive pro-Shia policies failed to unite the nation against the Sunnis of Isis, it does so by lavishing arms and money on militias made up of fellow Shia. In the latter, it did this by securing the survival of Isis’s number one recruiting sergeant, President Bashar al-Assad, amid a civil war costing almost 200,000 lives in which jihadis have tried to replace Syrian nationalists as the opposition to Mr Assad. Surely these policies must give pause before Tehran is invited to join a team whose members see them largely as hostile and destructive.

Mr Kerry’s approach is to pursue the shrinking possibility of reaching an agreement to limit Tehran’s nuclear programme to civil activities while also working to neutralise the toxic effects of its policies elsewhere. Iran itself probably sees any such agreement as a one-off: it may not really need nuclear weapons in any event but it does very much want to escape crippling sanctions. Yet under current management it is likely to pursue policies that project its own power in the region, inimical to the interests of the US and its regional partners – nuclear agreement or no.