"There is nothing more important in defining the framework for our nuclear activities than the leader's fatwa," he was quoted by state-funded broadcaster Press TV as saying. "This fatwa is our operational instruction."
Khamenei said last year that Tehran considers nuclear, chemical and similar weapons "a great and unforgivable sin."
The International Atomic Energy Agency said there may be certain military aspects to parts of Iran's controversial nuclear program, however. Inspectors during a December visit to Iran were denied access to the Parchin military complex outside of Tehran. Further IAEA talks are scheduled Wednesday.
The spokesman added that he was waiting for word from European leaders on the possible resumption of talks with the so-called P5+1 -- Britain, China, France, Russia and the United States plus Germany.
Iran denies allegations that its pursuing the technology needed to manufacture a nuclear weapon.