US, Iran clash over Tehran’s testing of limits in nuclear deal

The United States and Iran on Thursday clashed openly at the UN atomic watchdog for the first time since they signed a landmark nuclear deal last year, differing over Tehran’s repeated testing of one of the deal’s less strictly defined limits.

The International Atomic Energy Agency (IAEA), which is policing the deal, said Iran’s overstepping of the limit on its stock of a sensitive material for the second time this year risked undermining countries’ support for the agreement.

The victory of Donald Trump - a vocal critic of the deal - in the US presidential election also raised the question of whether his country would continue to support the accord, which restricts Iran’s nuclear activities in exchange for the lifting of sanctions against the Islamic Republic.

“Iran must strictly adhere to all commitments and technical measures for their duration,” US ambassador to the IAEA Laura Holgate said in a statement to the agency’s quarterly Board of Governors meeting.

The dispute centres on the part of the deal between Tehran and six major powers that limits Iran’s stock of heavy water, a material used as a moderator in reactors like the unfinished one it has at Arak that has been put out of use.

In contrast to strict limits elsewhere in the deal on materials including enriched uranium, the text says Iran should not have more heavy water than it needs, adding that those needs are estimated to be 130 tonnes. Western countries see it as a hard limit, and Iran argues it is not.