The head of the UN atomic watchdog will visit Iran on Sunday, the organisation said, ahead of an August 25 deadline for Tehran to answer long-held allegations of efforts to develop nuclear weapons.
Addressing these claims, long refuted by Iran, would be an important element in the comprehensive accord over Tehran's nuclear programme that Iran and world powers want to strike by November 24.
In its short statement on Friday, the International Atomic Energy Agency gave no details about what exactly Yukiya Amano would discuss with Iranian leaders and senior officials.
The Vienna-based watchdog said only that the visit, the Japanese Amano's first to Iran since November, was "part of the efforts to advance dialogue and cooperation" with Iran.
But it comes shortly before an August 25 deadline for Iran to provide the IAEA with information to clear up some of the many claims of past and possibly ongoing research into nuclear weapons by the Islamic republic.
These are Iran's alleged use of what the IAEA calls "large-scale high explosives experimentation" and suspected computer studies exploring what happens in a nuclear explosion.
These two out of around a dozen areas of alleged suspect activity by Iran -- mostly, but not only, conducted before 2003 -- were highlighted by the IAEA in a major report issued in November 2011.
Until now Iran has rejected out of hand all the claims as being based on faulty intelligence provided by the likes of the US Central Intelligence Agency (CIA) and Israel's Mossad.
Some analysts have also called into question some of the IAEA's assertions and whether the Vienna body has the legal right to conduct such a probe in the first place.
Iran denies seeking or ever having sought to develop nuclear weapons, saying that its nuclear programme, which has been steadily expanding for more than a decade, is purely for peaceful purposes.
One Vienna diplomat told AFP that Amano's visit will "hopefully catalyse progress" in the IAEA's probe into what the watchdog dubs the "possible military dimensions" of Iran's nuclear programme.
- UN General Assembly -
Iranian news agency IRNA, quoting Iran's ambassador to the IAEA, reported that Amano would meet President Hassan Rouhani during his one-day visit.
It comes ahead of a new round of talks between Tehran and the five permanent members of the UN Security Council plus Germany, expected before the UN General Assembly starts on September 16.
Those talks are aimed at securing a historic accord under which Iran scales back its nuclear activities in order to ease concerns that they are aimed at giving the Islamic republic the bomb.
In return Iran would be granted relief from painful UN and Western sanctions. Such a deal could finally put an end to a snowballing standoff that has been threatening to escalate into a war since 2002.
The deadline is November 24, a year after the agreement of an interim deal in Geneva partially freezing Iran's nuclear activities in return for minor sanctions relief.
The Institute for Science and International Security believes that it is vital for the sought-after deal that Iran answers the IAEA's questions, even if that means Tehran has to "come clean" in some way.
"The (PMD) issue is not the only stumbling block to a long-term deal -- there are plenty of others," ISIS analysts said in a recent report.
"However, unless there is verified assurance that Iran is no longer developing nuclear weapons ... any deal will be inadequate," it said.