Iran’s rulers maintain that the country’s nuclear programme is intended for purely peaceful purposes. Were the subject less serious, the dissimulation would be laughable.

John Kerry, on his first overseas trip as US Secretary of State, rightly spoke yesterday of the “finite time” available for international negotiations to resolve the issue. But there is a serious danger of under-reacting to Iran’s nuclear programme. It is crucial that Western governments maintain a unified diplomatic stance and persist with punitive sanctions. The alternative to defusing this emerging threat now, through peaceful pressure, will be to risk contending in the long term with a regime pursuing its goals through nuclear blackmail.

The emptiness of Tehran’s protestations can be succinctly stated. To generate electricity, it is not necessary for Iran to have its own uranium enrichment facilities; all that a peaceful country need do is buy uranium more cheaply on the open market. Yet Iran demands access to the full fuel cycle and lies about what it has. As long as a decade ago, Tehran stood exposed for building illicit and clandestine facilities, specifically a uranium enrichment facility at Natanz and a heavy water plant at Arak. These are not necessary for a civil nuclear programme but make sense for a military one.