"It is most strange that countries that initially supported Iran, changed their stance by approving the decision of the International Atomic Energy Agency, which is unfair and extremely unjust," Ali Akbar Hashemi Rafsanjani said, the Iranian News Agency, IRNA, reported.
He said Iran "is on the way of enriching uranium which is available in Iran for use only in medical, agricultural and scientific fields that are peaceful."
Rafsanjani's remarks came one day after IAEA's 35-nation board of governors adopted a resolution expressing "serious concern" at Tehran's decision to resume uranium conversion activities.
The resolution urged Iran to re-establish full suspension of all enrichment-related activities, after Tehran raised the stakes in the dispute by removing IAEA seals at a conversion facility in Isfahan.
Rafsanjani said Iran's decision to resuming uranium conversion was a great move.