France said it was still hopeful the original deal would be agreed but it is understood that neither Britain nor France and Germany will accept Iran’s new terms.

They believe Iran is trying to use the deal merely as a starting point to draw other countries into another protracted round of talks. During that time they think the Iranians could continue to enrich uranium and conduct more research on the scientific know-how necessary to turn it into a nuclear weapon.

“It’s like playing chess with a monkey,” said one diplomat close to the talks. “You get them to checkmate, and then they swallow the king.”