International Atomic Energy Agency chief Mohamed ElBaradei said on Thursday Iran must co-operate with the nuclear watchdog's efforts to monitor its atomic energy programme or face "serious implications".
"They know it's very important for the agency to come to a conclusion that the Iran programme is for peaceful purposes," he told reporters at the World Economic Forum.
"It would obviously have serious implications if they do not continue to co-operate fully with us in investigating the scope, nature, and content of that programme," ElBaradei added.
The United States suspects Iran of acquiring nuclear arms under cover of its atomic energy programme, which Tehran insists is for peaceful purposes.
ElBaradei has previously warned that Iran would be reported to the UN Security Council if it did not co-operate with the Vienna-based nuclear agency.
The IAEA head also said that he had no evidence of Iranian foreign "procurement" of equipment used to enrich uranium, but confirmed that the agency was looking into manufacturing of such equipment inside the country.
Diplomats have said this manufacturing was related to enrichment centrifuges.
"We haven't seen recent indications of (foreign) procurement. They are working on domestic manufacturing, that's something they told us," he said.
Earlier on Thursday, diplomats told Reuters that Britain, France and Germany were concerned about Iran's implementation of a pledge last year to cease uranium enrichment.
Diplomats say Tehran, despite the pledge, has continued to acquire large amounts of equipment for centrifuges.