International Atomic Energy Agency (IAEA) Director General Yukiya Amano smiles as he waits for a board of governors meeting to begin at the IAEA headquarters in Vienna, Austria June 6, 2016. REUTERS/Heinz-Peter Bader

PARIS (Reuters) - Iran has kept to a nuclear deal it agreed with six world powers last year limiting its stockpiles of substances that could be used to make atomic weapons, the head of the International Atomic Energy Agency (IAEA) told French daily Le Monde.

Confirming the findings of a confidential report by the U.N. agency seen by Reuters last month, IAEA Director-General Yukiya Amano said Tehran had observed the deal which was opposed by hardliners inside Iran and by skeptics in the West.

“The deal is being implemented since January without any particular problem,” he told Le Monde in an interview published on Saturday.

“There was a small incident in February: the stock of heavy water very slightly exceeded the limit set - 130 tonnes. But we immediately signaled that to Iran which took all the necessary measures,” he said.

Under its July deal with the United States, Russia, China, France, Britain and Germany, Iran is allowed to have 130 tonnes of heavy water, a moderator in reactors like the one it has disabled at Arak and a chemical it produces itself.

The stock briefly reached 130.9 tonnes, the agency reported in February.

“Apart from that, I can certify that Tehran respects its commitments to the letter. The Iranians are doing what they promised the international community,” Amano said.