The United States on Tuesday stepped up pressure on Iran over its nuclear programme, while Russia denied it had proposed letting Iran enrich small quantities of uranium.
The United States also renewed accusations that Iranian forces were crossing into Iraq, adding to instability in the country.
Ahead of talks with visiting Russian Foreign Minister Sergei Lavrov, the US administration reaffirmed that it would not agree to Iran carrying out any uranium enrichment -- a key stage in the development of a nuclear bomb.
Iran has rejected that position, insisting on continuing its small-scale enrichment activities, and that it is not building a nuclear weapon.
But Lavrov denied that Moscow had made a different proposal that would allow Iran to enrich small quantities of uranium while Russia handles the main processing tasks for Tehran and then retrieves the nuclear waste.
After meeting with US Secretary of State Condoleezza Rice, Lavrov said: "There is no compromise to the Russian proposal."
Rice also insisted that the Russian minister had made no new proposal during their talks.
Earlier diplomats in Vienna, where the International Atomic Energy Agency is discussing Iran, said Russia had proposed that Iran would be allowed small quantities of uranium, but would not get technology for large-scale enrichment that could be diverted for weapons use.
{{/usCountry}}Earlier diplomats in Vienna, where the International Atomic Energy Agency is discussing Iran, said Russia had proposed that Iran would be allowed small quantities of uranium, but would not get technology for large-scale enrichment that could be diverted for weapons use.
{{/usCountry}}Lavrov opened talks on Tuesday with President George W. Bush at the White House, where a spokesman reaffirmed support for the proposal for Russia to enrich uranium for Iran.