Opposition leader Mirhossein Mousavi has sharply criticised the outcome of Iran's talks with world powers this month, making clear he was against a proposal to send enriched uranium abroad, a reformist website reported.
The report came as Iran was expected later on Thursday to present its official position on a U.N.-drafted plan for it to ship much of its uranium stockpile abroad for further processing, meant to help ease tensions over its nuclear drive, Reuters reported.
The draft agreement was hammered out by U.N. nuclear agency chief Mohamed ElBaradei in follow-up talks to an Oct. 1 meeting between Iran and six world powers in Geneva, where Iran also agreed to open a new enrichment site for U.N. inspections.
Senior Iranian lawmakers have cast doubt on the fuel plan, saying Tehran should import the fuel it needs for a research reactor rather than sent its stockpile out of the country.
Iranian media say Tehran will accept the framework of the proposal but also seek changes to it, a move that could unravel the plan and expose the Islamic Republic to the threat of harsher sanctions.
"The discussions in Geneva were really surprising and if the promises given (to the West) are realised then the hard work of thousands of scientists would be ruined," Kaleme website quoted Mousavi as saying, in a clear reference to the fuel plan.
"And if we cannot keep our promises then it would prepare the ground for harder sanctions against the country," he said in a meeting with pro-reform cleric Mehdi Karoubi on Tuesday evening, Kaleme reported.
The West suspects Iran is seeking to develop nuclear bombs. Tehran denies this and says its programme is aimed at generating electricity.
Under the draft deal put forward by ElBaradei after consultations last week in Vienna with Iran, the United States, France and Russia, Iran would send low-enriched uranium (LEU) abroad for processing and eventual use in a research reactor.