The Russian proposal "will be reviewed seriously and enthusiastically," Javad Vaeedi, the deputy head of Iran's Supreme National Security Council, told the ISNA students news agency on Wednesday.
The remarks were the most positive yet by a senior Tehran official about Moscow's offer to form a joint venture with Iran to enrich uranium in Russia.
The Russian offer is backed by the United States and the European Union.
It is aimed at easing international concerns that Tehran could make atom bombs from highly-enriched uranium.
Iran says it only wants to enrich uranium to a low grade, suitable for use in nuclear power reactors.
"In our opinion the Russian proposal could revive some of the unimplemented regulations of the nuclear Non-Proliferation Treaty for transferring nuclear technology to countries which do not have access to this technology and break the scientific monopoly of this issue," Vaeedi said.
Striking a much softer tone than recent comments by other Iranian officials, Vaeedi said the Russian proposal could be studied in the framework of an existing agreement with Moscow on supply of enriched uranium for Iran's first atomic reactor at Bushehr, due to come onstream in late 2006.
"The new proposal could be studied and its economic, technical and scientific dimensions clarified. The amount of participation of the Iranian side in this plan will be an important indicator," he said.
"Whatever meaning the Russian proposal has, it does not mean depriving Iran of its rights"
Deputy head of Iran's Supreme National Security Council
"Whatever meaning the Russian proposal has, it does not mean depriving Iran of its rights," he added.
Previously, Iranian officials had poured cold water on the Russian proposal, saying they would not accept any plan which did not allow Iran to carry out a full nuclear fuel cycle, including enrichment, on its own soil.
But EU diplomats and arms control experts have noted that Tehran had stopped short of outright rejection of the plan, which could weaken Russian opposition to EU and US efforts to refer Iran to the UN Security Council for possible sanctions.
They say Iran may be willing to drag out talks about the Russian proposal to buy time and good favour.
Face-to-face nuclear negotiations between Iran and the EU trio of Britain, Germany and France resumed in Vienna this month and are due to take place again in January.