For Mr Salehi, a stint as Iran's representative to the International Atomic Energy Agency (IAEA) was a fast-track to being appointed foreign minister in 2011.

BBC: Iran's nuclear ambitions stalk presidential election

Mr. Blix was head of the International Atomic Energy Agency (IAEA) in Vienna from 1981-97.

CENTERFORSECURITYPOLICY: Unable to verify, unworthy of trust

The deal now needs to be approved by the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), as well as by the 45-nation Nuclear Suppliers Group, which regulates global civilian nuclear trade.

BBC: India gives nuclear plans to IAEA

Last year, the IAEA (International Atomic Energy Agency) found particles of man-made uranium at the al-Kibar site in Syria, which was destroyed by Israeli missiles in September 2007.

BBC: Uranium found at second Syria site - IAEA

The International Atomic Energy Agency (IAEA) has previously said it suspects the Parchin site may be being used for nuclear weapons-related testing.

BBC: Iran nuclear: Israel's Netanyahu warns on attack timing

The This World team gain exclusive behind-the-scenes access to the UN's nuclear watchdog in Vienna, the International Atomic Energy Agency (IAEA), as they scrutinise Iran's nuclear capability.

BBC: Iran's HQ for the Atomic Energy Organisation