Iran has begun to answer long-held allegations of efforts to develop nuclear weapons ahead of an August 25 deadline, the UN atomic watchdog's chief said on Monday.
Returning from Tehran, where he met with President Hassan Rouhani and top Iranian nuclear officials, IAEA chief Yukiya Amano said that Iran had started carrying out crucial measures agreed in May to clear up claims it has done research into nuclear weapons.
This included two measures related to the so-called "possible military dimensions" (PMD) of Iran's nuclear programme, which Tehran insists is entirely peaceful.
"We have started the implementation of the five measures including PMD," Amano told journalists on arrival at Vienna airport.
He did not give any details about the process however and refused to say if Iran would be able to complete it by the deadline next Monday.
"We have started and that is important and I expect that progress will be made over the next week," Amano said, adding that some of his team had stayed behind to continue inspections of Iranian nuclear facilities.
Answering the PMD allegations is an important part of a comprehensive agreement that world powers and Iran are trying to nail down by November 24.
In May, the International Atomic Energy Agency announced Tehran had for the first time in six years shared information regarding this issue with the nuclear watchdog.
Iran insists its nuclear drive — which has been expanding steadily for the past decade — is solely for civilian purposes but the West has long believed it is seeking an atomic bomb.
On Monday, Amano noted that the IAEA had "received additional clarification" from Iran regarding sophisticated explosive detonators that can be used in a nuclear bomb but also have other applications.
He added that new measures — a fourth series to follow the ones from May — were also in the works.
"We have started the discussion on the new practical measures to be taken up as a new step," Amano said.
"I hope and I expect that we can reach agreement soon," he added.
The IAEA-Iran efforts run parallel to talks with the five permanment members of the UN Security Council and Germany aimed at reaching a historic deal to get Iran to scale back its nuclear activities.
A new round of talks between Iran and the so-called P5+1 powers is expected before the UN General Assembly on September 16.