By Anton La Guardia, Diplomatic Editor
Britain last night gave Iran two months to come clean about its nuclear programme and halt work on enrichment of uranium or face a demand for United Nations sanctions.
After more than a year of "engagement" with Teheran over its nuclear ambitions, which America believes are designed to make a nuclear bomb, a senior British official said European countries were running out of patience.
The governing board of the International Atomic Energy Agency meets next week and the official said western countries would seek a resolution setting the board's next meeting in November as the "point of decision".
The aim is to increase pressure on Teheran although an unspoken objective is to defer any crisis until after the US presidential election early in November.
Some British officials would like to postpone a showdown with Teheran until after Iraq's elections in January to reduce the chances of Iran stirring political violence.
But the three European countries involved in the talks - Britain, France and Germany - are under strong pressure from America to stand up to Teheran.
This summer, Iran reneged on key aspects of a deal to suspend uranium enrichment, a key process that can be used to produce fissile material for either nuclear fuel or atomic bombs.