"The designs for the first new nuclear (enrichment) site will be done this year," Ali Akbar Salehi told ILNA news agency.
"The location of this nuclear site has not yet been finalised. After the president's approval, a decision will be made in this regard."
On Monday, Mojtaba Samareh Hashemi, a senior adviser to Ahmadinejad, said the president had "approved the locations of the new nuclear sites" and the "construction at these sites will start with his order."
But Hashemi also clarified that the designs of the new plants were currently under study.
In November 2009, a defiant Ahmadinejad announced Iran would build 10 new uranium enrichment plants after Tehran was censured by the UN nuclear watchdog for having built a second such facility near the Shiite shrine city of Qom.
Salehi himself said in April that plans for two new enrichment plants had been submitted to Ahmadinejad and their construction would start in the first half of the Iranian year, which runs to March 2011.
Iran currently enriches uranium at the central city of Natanz. According to the UN nuclear watchdog's February report, it has installed 8,610 centrifuges at the plant.
The Islamic republic says the overall capacity of the Natanz plant is 50,000 centrifuges, the machines which enrich uranium for nuclear use at supersonic speed.
Salehi has also said in the past that the new enrichment plants will be located inside mountains to guard against aerial attacks.
The United States and its ally Israel have never ruled out a military strike against Iran's nuclear facilities to halt its atomic programme which they charge masks a weapons drive. Iran denies the allegations.
