Britain, France and Germany will give to Iran next week an incentives package aimed at convincing Tehran to give up nuclear ambitions, US officials said.
Iran says no international body can force it to end enrichment
"The EU Three have indicated they will be presenting their ideas to Iran next week," State Department spokesman Tom Casey told Reuters.
The offer includes a commitment to resume stalled talks on an EU-Iran trade agreement, diplomats said.
Iran says its nuclear programs are peaceful and only to generate power.
The talks between the US and the EU trio come amid a mood of some desperation among Western policy makers over Iran's nuclear programme, says BBC News Online's Paul Reynolds.
Efforts to get Iran to abandon its enrichment activities have been a failure so far, yet prospects of imposing effective sanctions on Iran through the UN Security Council are uncertain to say the least.
There is no great optimism that an offer to Iran would work given Iran's insistence that it will develop an enrichment capability, which it says will be used only for nuclear fuel, not for nuclear weapons, our correspondent adds.
The latest incentives are also thought to include guarantees that Iran will have access to nuclear
fuel from Russia.
Iran restated its intentions again this week.
Its Foreign Minister Kamal Kharrazi said: "The time has come for Europe to take a step forward and suggest that our legitimate right for complete use of nuclear energy is recognised (in exchange for) assurances that our programme will not be diverted toward weapons."
Our correspondent says Britain, France and Germany feel there is a window of opportunity ahead of a meeting of the UN nuclear agency, the International Atomic Energy Agency, on 25 November.