All those who were writing off Barack Obama last week as a foreign policy lightweight may now reflect at leisure on how he has achieved two major objectives in almost as many days: Russia is back on side, for now at least, thanks to his decision to re-model European missile defence. And China is now isolated in the security council in opposing new sanctions on Iran – a position it always tries to avoid on any major issue, and which it may now find untenable.

Today’s disclosure, and the concomitant conclusion that Iran’s leaders are congenital double-dealers, will further spur the debate among regional neighbours, in particular Saudi Arabia, Turkey and Egypt, about acquiring nuclear capabilities of their own. Thus does the feared, fabled Middle East nuclear arms race inch closer…

Yet Obama’s bid to open a dialogue with Iran – the so-called “unclenched fist” – may, conversely, be strengthened by these latest developments. Iran has been placed on the back foot. It has been caught lying, again. It cannot convincingly pretend, even to its central Asian friends and fellow travellers like Venezuela’s Hugo Chávez, that it’s a mere innocent victim of Washington’s malice.

Nor can the regime easily tell its own much-abused, much-deceived people – and their moderate and reformist representatives in the Majlis – that it’s all a foreign plot. This bombshell will weaken supreme leader Ali Khamenei, Ahmadinejad, chief negotiator Saeed Jalili, and the rest of Tehran’s hardliner crew abroad and at home although, as usual, they will try to bluff their way through.