The United States and Russia have ruled out an Iranian proposal to allow Tehran to run its own small-scale uranium enrichment programme.
Iran insists its nuclear programme is purely peaceful
Iran had suggested it might be allowed to enrich small quantities of uranium for research purposes while importing most of its nuclear fuel from Russia.
However, the US opposes allowing Iran to enrich any uranium.
Speaking in Washington, Russia's Foreign Minister Sergei Lavrov also rejected a deal.
Mr Lavrov said Moscow's proposal for Iran to enrich uranium on Russian territory depended on Iran's full compliance with the requirements of the UN nuclear agency.
The International Atomic Energy Agency wants Iran to suspend uranium enrichment altogether. Its board is currently meeting in Vienna to consider Iran's case.
It voted last month to report Iran to the UN Security Council for failing to disclose details of its nuclear activities.
Last week, Tehran suggested a compromise deal in which it would be allowed to enrich a small amount of uranium for research purposes, in return for accepting the Russian proposal.
However, US Secretary of State Condoleezza Rice said the only deal she backed was the original Russian proposal.
"This is not an issue of Iran's right to civil nuclear power, it is that there needs to be a way to provide for civil nuclear power that does not have a proliferation risk," she said after talks with Mr Lavrov.
Mr Lavrov said there was "no compromise" to the Russian proposal.
Western powers believe Iran wants to develop nuclear arms, a claim it denies.
Tehran insists it has the right to develop its nuclear sector to produce energy for civilian purposes.
Three years of negotiations between Iran and the EU have brought no significant result, and Iran resumed enrichment in January after a two-year hiatus.
Earlier, Iranian President Mahmoud Ahmadinejad said the West should compensate Iran for its suspension of nuclear research, as a way of building trust.
However, he failed to mention that Iran's suspension of uranium enrichment two years ago - the basis of his call for compensation - had been voluntary, the BBC's Frances Harrison reports from Tehran.
A senior military commander warned on Monday that the Iranian military would turn the country into a killing field for any enemy aggressor.
There is now more talk from Iranian officials of preparing people psychologically for confrontation with the West, our correspondent says.
But Iranian television has accused Western media of exaggerating the dispute over Iran's nuclear ambitions, our correspondent says.