Negotiators from the European Union's three biggest powers have begun talks with Iranian negotiators to try to persuade Iran to abandon nuclear technology that could be used to make weapons.
The meeting was the latest step in a diplomatic initiative that began in October 2003 when Iran first promised to suspend all work linked to the enrichment of uranium, a process of purifying uranium for use as fuel in power plants or bombs.
This initiative collapsed early last year but was revived in December. Negotiators on both sides in today's talks - senior officials a few notches below ministerial level - said they expected tough negotiations as both parties had adopted hard positions.
"We both have our entrenched positions," one European diplomat close to the talks said. "With the Americans on board, the EU three couldn't move if they wanted to."
Sharing US suspicions that Tehran may be planning to develop nuclear arms, France, Britain and Germany are offering Iran political and economic incentives to terminate and dismantle its uranium enrichment programme as an "objective guarantee" that it is not a front to develop an atomic bomb.
Tehran refuses to give up the programme and has offered to permit increased inspections by the UN's International Atomic Energy Agency (IAEA) and to limit its enrichment to levels far below the high levels of purity needed to fuel an atomic weapon.
"Iran is ready to give objective guarantees to prove that it will not divert nuclear fuel to military uses, not seek weapons of mass destruction," Hossein Mousavian, a senior Iranian negotiator, told Iranian state radio on Tuesday.
The Iranians have made it clear that the guarantees will not include a termination of the programme. This is unacceptable to the EU which wants the programme scrapped.
Mousavian also said Iran may pull out of the talks if it decides insufficient progress has been made.
"The best that can come out of this meeting is an agreement to keep talking," a diplomat close to the talks said.