The leading powers were forced to cancel a meeting due to be held on Wednesday on the Iranian nuclear threat after Russia said the talks were not urgent, in a further sign of Moscow’s frostier relations with the west after the Georgia crisis.

Foreign ministers from the US, China, Russia, France and the UK – the five permanent, veto-holding members of the United Nations Security Council – and Germany were due to meet to discuss further sanctions aimed at reining in Tehran’s nuclear programme.