But chief nuclear negotiator Ali Larijani reiterated Iran's stance that it was ready to hold talks on its nuclear program. Six world powers have offered a package of economic incentives to the Islamic Republic if it halts uranium enrichment.
"Iran will continue its uranium enrichment. We want to produce our own nuclear fuel," Larijani was quoted as saying by the student news agency ISNA. "We will never stop it."
The U.N. Security Council has told Iran to suspend atomic fuel work by August 31 or face possible sanctions. The West suspects Iran is secretly trying to make nuclear weapons but Tehran says its only aim is to generate electricity.
Uranium enrichment can be used to produce fuel for nuclear power stations or material for nuclear bombs.
The Islamic Republic says international sanctions would only propel oil prices higher still, damaging the economies of the industrialized world.
"Any measure to deprive Iran of its right will not change our mind about our aim," said Larijani.