Kamal Kharrazi said concerns voiced by the United States that Iran was developing nuclear technology for military purposes were unfounded.
The International Atomic Energy Agency will send inspectors to check Iran's nuclear facilities in February, after Tehran postponed a visit scheduled for this month.
Fresh concerns about Iran's nuclear programme were raised this week after satellite photographs showed developments in two new areas, which US officials said were suspicious.
Mr Kharrazi told official state media: "Iran has no plan to produce nuclear weapons, and all efforts in this field are intended for peaceful means."
'No secret'
He said Iran needed nuclear power plants to produce 6,000 megawatts of electricity within the next 20 years to meet demand.
"The activities of the Islamic republic are totally transparent, clear and peaceful and there is no secret and obscure point about it," he said.
"These two centres are aimed at producing necessary fuel for nuclear power plants" that will supply the electricity.
US officials said on Friday that facilities at Arak and Natanz spotted in commercial satellite photographs taken in September were both of a type that could be used to help build a nuclear weapon.
A nuclear power plant is already being built, with the help of Russian technicians, at the port of Bushehr, and is scheduled to begin operating in 2004.
American intelligence officials argue that a weapons programme is the only reason why an oil-rich state like Iran would need a nuclear power plant.