World powers will meet in London today to discuss a package of incentives and threats drafted by European countries aimed at defusing a crisis over Iran's nuclear programme.
British Foreign Secretary Margaret Beckett
Senior officials from UN Security Council permanent members China, Russia, the United States, France and Britain, plus Germany, will try to narrow divisions over how to proceed to persuade Tehran to halt its uranium enrichment work.
The head of Russia's atomic energy agency said in Washington he hoped for a "major breakthrough" on the nuclear row at the London meeting but a US official said that more talks may be needed to reach agreement.
"I hope that this proposal would be a major breakthrough in this issue," Sergei Kiryenko said after talks with Secretary of State Condoleezza Rice and other senior US officials.
But he gave few details and it was unclear whether serious differences had been resolved between Washington and Moscow over US demands that Iran face sanctions, resisted by Russia, if it continues to defy the international community.
The official, who spoke anonymously, said he did not expect "full closure" at the London meeting and that there likely would be "more talks next week."
Washington and some western nations suspect Iran's nuclear programme is a cover for efforts to develop an atomic bomb.
But the Islamic Republic says it is developing nuclear technology for civilian power generation. It has said it will not stop its nuclear work, even for incentives
US President George W. Bush said countries had to work together to encourage Tehran to halt its nuclear programme.
"Obviously we'd like to solve this issue peacefully and diplomatically, and the more the Iranians refuse to negotiate in good faith the more countries are beginning to realise that we must continue to work together," Bush said.
But Mr Bush said Iran had so far not shown signs of agreeing.
"We're spending a lot of time working with our Russian friends in particular to make it clear to them that Iran is showing no good faith," he said.
Foreign Secretary Margaret Beckett told parliament: "It is the intention to encourage Iran to see the nature of the choice that lies before it."
The package is likely to include an offer of a light-water reactor and an assured supply from abroad of fuel for civilian atomic plants so Iran would not have to enrich uranium itself.
Enriched uranium can be used as a nuclear fuel, but is also a key component of atomic weapons.
The package will also warn of possible sanctions if Iran, the world's fourth-biggest oil producer, refuses the offer.