Western powers are trying to "cheat" Iran through a UN-brokered deal for supplying nuclear fuel to a Tehran research reactor, Ali Larijani, Iran's parliament speaker, has said.
Larijani's comments on Saturday add to growing criticism by Iranian legislators levelled at the UN-drafted agreement.
"Westerners are insisting to go in a direction that speaks of cheating and are imposing some things on us," Larijani told Iran's ISNA news agency.
"They are saying we will give you the 20 per cent [enriched uranium] fuel for the Tehran reactor only if you give us your enriched uranium," he said.
"I see no links between providing the fuel for the Tehran reactor and sending Iran's low enriched uranium abroad."
The draft deal by the UN's International Atomic Energy Agency (IAEA) requires Iran to cut its atomic stockpile by sending it abroad for reprocessing.
The agreement requires Iran to send 1.2 tonnes of its known 1.5-tonne stockpile of low-enriched uranium to Russia and France by the end of the year, Western diplomats say.
Abroad, the uranium would be further processed, in a way that would make it hard to use for warheads, before being returned to Iran as fuel plates to power a Tehran reactor that makes radioactive medical isotopes but is due to run out of its imported fuel in a year.
Tehran missed a Friday deadline for responding to the deal, saying its answer would be given next week.
Many Iranian officials have suggested that instead of accepting the draft, Iran should buy nuclear fuel from abroad.
Buying enriched uranium abroad would not reduce Iran's domestic stockpile. It would also require sanctions imposed on Iran since 2006 to be waived to allow it to import the material.
Heshmatollah Falahatpisheh, another leading Iranian legislator, said the lifting of sanctions should be part of any deal Iran made on its nuclear programme.
"Any nuclear fuel deal with the West ... should come with relinquishment of sanctions on Iran, particularly a lifting of sanctions on raw uranium imports," he was reported by the semi-official ILNA news agency as saying.
The debate comes as UN inspectors left Vienna for Iran to examine a nuclear site at Qom.
The IAEA deal requires Iran to send 1,100kg of low-enriched uranium, which is about 70 per cent of its stockpile, to Russia by the end of the year.
After further enrichment there, the uranium would be sent to France to be converted into fuel to be used in Iran's medical research programme.
The deal is believed to prevent Iran from developing nuclear weapons, as 1,000kg is the amount of low-enriched uranium needed to produce a single nuclear bomb.
The four-strong inspection team is due to arrive in Tehran early on Sunday and head out to the site in hills 160km south of Tehran for a stay likely to last several days.
The revelation of the Qom facility - which Western nations say came only as a result of investigations by their intelligence agencies - has heightened Western fears of a covert Iranian programme to develop atomic bombs.
Iran denies the accusation and says its nuclear programme is for civilian purposes only.
The IAEA inspectors intend to compare engineering designs of the Qom facility, to be provided by Iran, against the actual facility.
They will also interview employees and take environmental samples to verify that the site has no military dimension.