Iran says it will reject any proposal to end its work on uranium enrichment, a process that could be used to make nuclear weapons.
Hossein Mousavian, a senior Iranian official involved in the nuclear negotiations, has told state television his country will not accept any plan that requires it to drop what he calls "its legitimate right" to enrich uranium to make fuel.
European Union diplomats have said they are seeking U.S. and Russian support for a deal that would ask Iran to give up uranium enrichment in return for technical and economic assistance.
Iran has denied U.S. allegations it has military nuclear ambitions, saying its atomic program is solely dedicated to meeting high demand for electricity.
Uranium, enriched to a low level, can be used to fuel nuclear power stations such as one Iran is building at the southern port of Bushehr. However, if enriched further, it can be used in nuclear warheads.