President Hassan Rouhani said Sunday that despite "thousands of hours" of inspection, the UN's atomic watchdog has found no evidence of military objectives in Iran's nuclear drive.
His remarks came on the eve of an International Atomic Energy Agency board of governors meeting in Vienna, on the sidelines of which Iran will hold expert-level talks with world powers.
Western powers "all know that nuclear science in Iran follows a peaceful path", Rouhani said in a speech broadcast on state television.
"The agency has conducted thousands of hours of inspection, and announced it has not found any diversion from the peaceful use (of nuclear technology) to military purposes."
In its latest report on Iran in late February, the IAEA said Iran was sticking to a nuclear freeze it agreed under a November interim deal with world powers.
The watchdog's report came a month after the deal came into force.
Iran and the so-called P5+1 group of world powers are seeking to reach a lasting accord that would allay Western suspicions that Tehran's nuclear activities mask military objectives.
As part of such a comprehensive deal, the six seek to pressure Iran over its ballistic missile programme, which could theoretically provide Tehran with a device to deliver a nuclear warhead, should it choose to build one.
Rouhani on Sunday defended the programme, saying it has "always been defensive in nature, and will always remain so".
On Saturday, Rouhani had called for calm amid provocative rhetoric from Iranian hardliners.
"Sometime one does not seek war but talks as if one does, and this is seen as a threat to other parties. This is an unnecessary provocation," he told military personnel and defence ministry officials.
"The Islamic Republic of Iran's foreign policy is based on detente and building trust," he added.
Since taking office in August, Rouhani has vowed to rebuild strained relations with the West.