Vienna International Centre, which houses U.N. headquarters in city, and is a venue of latest round of talks with Iran on its disputed nuclear programme, is pictured in Vienna

The Vienna International Centre, which houses the United Nations (U.N.) headquarters in the city and is a venue of the latest round of talks with Iran on its disputed nuclear programme, is pictured in Vienna July 2, 2014.

The Vienna International Centre, which houses the United Nations (U.N.) headquarters in the city and is a venue of the latest round of talks with Iran on its disputed nuclear programme, is pictured in Vienna July 2, 2014. REUTERS/Heinz-Peter Bader

Iran, world powers resume push for nuclear deal by July 20