An adviser to Iran's supreme leader urged world powers to formally recognise its nuclear rights to bring about a "favourable result" at talks on its atomic programme this month.
Deflecting Iranian pressure in talks last month, western countries declined to accord any such recognition, saying Tehran had no automatic right to enrich uranium because of its previous violations of the nuclear Non-Proliferation Treaty.
Iran says that under its treaty membership, it can develop a full nuclear fuel cycle for peaceful purposes including the enrichment of uranium, a process that yields fuel for power stations or bombs, depending on the level of refinement.
"I hope the P5+1 group recognises Iran's inalienable nuclear right within the framework of the NPT and refrains from sitting on the sidelines," Iran's state news agency quoted Ali Akbar Velayati, an aide to Ayatollah Ali Khamenei, as saying.
"By accepting Iran's right to use peaceful nuclear energy, the forthcoming talks in Moscow should reach a favourable result."
Ayatollah Khamenei, who has total command over Iran's nuclear policy, has publicly forbidden the development of nuclear weapons. Iran says it is enriching uranium only for civilian energy.
Western nations suspect that the Islamic Republic's higher-grade uranium enrichment is part of a clandestine programme to develop the material and components needed for a capacity to produce nuclear arms.
Despite Velayati's firm line, diplomats say Iranian negotiators were forthcoming at the talks in Baghdad - in contrast to previous failed negotiations - and believe Ayatollah Khamenei has given them a freer hand to explore a deal.
Another round of talks has been scheduled for June 18-19 in Moscow. Last week the US secretary of state, Hillary Clinton, indicated the meeting would be crucial because of Washington's need to see "concrete actions".