The five permanent members of the U.N. Security Council -- the United States, Britain, France, Russia and China -- along with Germany have called on Iran to halt production of uranium enriched to 20 percent, which Iran says it needs for medical research.
Western powers, however, say it's a benchmark that would make it easier to reach the 90 percent purity needed for a nuclear weapon.
Fereydoun Abbasi, the head of the Atomic Energy Organization of Iran, said Tehran has the right to a uranium enrichment program.
"The Islamic Republic of Iran will produce 20 percent enriched fuel to the amount that it needs and as long as there is a need for it," he was quoted by the semiofficial Fars News Agency as saying.
U.N. nuclear inspectors left Iran last week without gaining access to the Parchin military complex outside of Tehran. The International Atomic Energy Agency there were questions about nuclear activities there.
Iranian Foreign Ministry spokesman Ramin Mehmanparast said Tuesday that Tehran was looking for ways to ally the IAEA's concerns.
"We will take measures which can lead to easing the IAEA concerns and you will witness its details, if we reach a comprehensive agreement which recognizes our rights," he said.