Russia says it again has presented to Iran a proposal for reprocessing uranium in Russia from Iran's nuclear plants.

The Foreign Ministry, in a statement, said its embassy in Tehran Saturday presented Iranian authorities with a note saying that its offer for setting up a joint Russian-Iranian uranium enrichment facility remains valid.

Iran has turned down previous Russian suggestions, insisting it has the right to enrich uranium and produce nuclear fuel domestically despite international efforts to curb its nuclear program.

The United States and the European Union have expressed grave concerns that Tehran will use its nuclear program as a cover for developing atomic weapons.

Under a deal signed earlier this year, Moscow agreed to supply enriched uranium fuel for Iran's Bushehr reactor. But it also demanded the return of spent fuel, to prevent Tehran from reprocessing it into bomb-grade material.