Britain, France and Germany are expected to meet on Wednesday in London with American, Russian and Chinese officials to discuss a package of incentives for Iran if Tehran curbs its nuclear ambitions, European diplomats said.
The meeting has been delayed several times among senior foreign ministry officials from the six nations, five of them UN Security Council members with veto power.
But diplomats from the three European nations, speaking on condition of anonymity, said they now expected the session to be held on Wednesday in London.
The three European nations are drawing up a package that is expected to include a European light-water reactor and some form of security assurances in return for a halt to uranium enrichment.
Iran said in April it had successfully enriched uranium for the first time, a process that has both peaceful and military uses. Iran says it only wants to make fuel for nuclear power stations but the West suspects this is a cover for bomb making.