Did Barack Obama have a chat with Karpov and Kasparov before he announced last week that he was abandoning Bush-era plans to locate a missile shield in Eastern Europe? He was quick – and right in the view of many defence experts – to reassure critics that far from leaving America's allies more vulnerable, his policy shift would clear the way for a much smarter system that would actually do more to shield southern Europe and the Middle East from short-range missile attack by Iran.

What he didn't state publicly was that his policy shift was also a carefully timed turn on the diplomatic chessboard that could arm him with a simultaneous weapon to contain Iran, not via interceptors and radars, but economic sanctions.

Containing Iran's nuclear ambitions peacefully is in turn part of a bigger jigsaw aimed at convincing Israel not to bomb Iran's nuclear plants, kick-start the moribund Middle East peace process and maybe even eventually establish the basis for a "grand bargain" around a future settlement in Afghanistan. Much of the above, especially any real progress between Israel and the Palestinians remains blocked for the time being. Benjamin Netanyahu's intransigence on settlements has made sure of that.

But against the backdrop of the theatrics of the UN General Assembly, Obama can still claim he has secured two big gains on Iran. He persuaded yesterday's special summit of the Security Council to back a resolution that ratchets up pressure on the Islamic Republic. And he extracted a strong hint from Russia that Moscow might back economic sanctions if nuclear talks with Iran next month make no progress. Nobody realistically expects those talks to deliver the kind of concessions from Tehran that would constitute "progress".

Moscow has long made clear its total hostility to the idea of what Hillary Clinton calls "crippling" sanctions or even of isolating Iran in the absence of proof that it is manufacturing a nuclear bomb. This week Dmitry Medvedev uttered the words Mr Obama wanted to hear. Sanctions rarely deliver results, said Mr Medvedev, but in some cases "they are inevitable".

It was hardly a coincidence the U- turn came so soon after Washington shelved the missile defence plan in Russia's backyard. Whether Russia would actually go along with an oil embargo when the time comes, is another matter. There is also the obstacle of China's veto. But if Russia joined the Western-led move, China could at least be persuaded to abstain.