The United Nations headquarters building is pictured in Vienna

The United Nations headquarters building (Vienna International Centre) is pictured in Vienna May 14, 2014. Six world powers and Iran launch the decisive phase of diplomacy over Tehran’s nuclear work during three-day talks starting in the VIC in Vienna on Wednesday, with the aim of resolving their decade-old dispute by July 20 despite skepticism a deal is possible. REUTERS/Leonhard Foeger (AUSTRIA – Tags: POLITICS ENERGY)

U.N. report to show Iran complying with nuclear deal: diplomats