The head of the UN atomic watchdog said Tuesday that he has signed with Iran a "roadmap" for probing suspected efforts to develop nuclear weapons, a key part of an overall accord with major powers.

"I have just signed the roadmap between the Islamic republic of Iran and the IAEA for the clarification of past and present outstanding issues regarding Iran's nuclear programme," International Atomic Energy Agency chief Yukiya Amano said ahead of the expected announcement of a historic deal with major powers.