Talks on Wednesday with the European Union (EU) about Iran's nuclear program have only a 50-50 chance of success, a leading Iranian negotiator has warned.

Speaking after preparatory talks in Brussels on Tuesday, Hossein Mousavian, top nuclear negotiator and member of Iran's Supreme National Security Council, said there were no guarantees of avoiding a breakdown in negotiations.

"(There) is a 50-50 percent chance of success," he told reporters, "These talks were more difficult and complicated than ever."

The official-level talks were aimed at preparing for top-level negotiations in Geneva on Wednesday between Iran and the EU, which was represented by the foreign ministers of Britain, France and Germany, along with EU foreign policy head Javier Solana.

The talks were called following threats by Iran to resume enriching uranium. It says it is entitled to do so, but is ready to offer guarantees that its nuclear program will be exclusively for civilian purposes.

The EU has warned Tehran that a breakdown in talks could lead to a referral to the UN Security Council.

"There was a clear reaffirmation that the Iranians have to respect the commitments they entered into last November under the Paris agreement," Luxembourg Foreign Minister Jean Asselborn said after chairing an EU foreign ministers meeting on Monday.

"This is very important for further relations between the EU and Iran," said Asselborn, whose country holds the rotating EU presidency.

Tehran suspended enrichment activities in last November and began talks with the EU big three of Germany, France and Britain.

(Xinhua News Agency May 25, 2005)