Reports about Zarif’s temper first emerged in the Iranian press last November, when the United States and Iran agreed to extend talks through June of this year.

Zarif is said to “frequently shout at Western diplomats” with such force that bodyguards have been forced to enter the negotiation room.

During one incident described by Iranian officials to the press, European Union Foreign Policy Chief Catherine Ashton, a chief western negotiator, admitted that Zarif had been shouting, and she had gotten used to it.

Abbas Araqchi, an Iranian diplomat who is also a member of the negotiating team, is reported to have said in an interview that during past negotiations in Geneva, Zarif “shouted” at Kerry and spoke to him in a manner “unprecedented” in the history of U.S. diplomacy.