International Atomic Energy Agency (IAEA) Director General Yukiya Amano prepares for a board of governors meeting at the IAEA headquarters in Vienna June 2, 2014. The head of the U.N. nuclear watchdog said on Monday Iran's engagement with the IAEA in recent months had helped it "gain a better understanding" of Tehran's disputed nuclear programme. REUTERS/Heinz-Peter Bader (AUSTRIA - Tags: POLITICS ENERGY HEADSHOT)