Diplomats from France, Britain and Germany will meet their Iranian counterparts in Paris today to discuss an EU offer of incentives in exchange for a termination of Iran's uranium enrichment programme.
Iranian negotiators will offer to temporarily suspend their enrichment program, which Washington believes will be used to produce fissile material for atomic weapons, for around six months, diplomats said.
But this proposal is unacceptable to the European Union's "Big Three" powers, who want Iran to agree to an "indefinite" suspension, diplomats said.
"We still want a termination of the enrichment program and all related activities," a Western diplomat close to the EU-Iran talks said in Vienna. "I don't expect a breakthrough."
International Atomic Energy Agency (IAEA) chief Mr Mohamed ElBaradei has encouraged Iran to reach a deal with the Europeans and has even offered to guarantee Iran's supply of nuclear fuel if it abandons its fuel production capabilities, diplomats said.
But Tehran has insisted that uranium enrichment, a process of purifying uranium for use as fuel in atomic power plants or in weapons, is a sovereign right that it will never abandon.
If no deal is struck ahead of a November 25th IAEA meeting on Iran's nuclear program, the EU is expected to support Washington's demand for a referral to the UN Security Council and possible economic sanctions.