Iran's top nuclear negotiator called Monday for a "new approach" in ties with the UN atomic watchdog, kicking off a series of meetings preparing for tough talks with world powers next week.
"We think that it is time to take a new approach to resolve questions between Iran and the IAEA," Abbas Araqchi said in Vienna as he met with International Atomic Energy Agency chief Yukiya Amano.
He called the meeting, the first in a series of gatherings in Vienna this week meant to pave the way for talks with the so-called P5+1 group in Geneva on November 7-8, "very useful and constructive".
Amano said the talks were a "very important opportunity" and that it was "very important for all of us to show concrete progress".
Iranian and IAEA officials went into separate meetings Monday -- set to continue Tuesday -- on allegations that prior to 2003, and possibly since, Tehran carried out nuclear weapons research.
On Wednesday and Thursday, a seven-member expert Iranian team will meet with counterparts from the six powers -- the so-called P5+1 of the United States, Britain, France, China and Russia plus Germany.
Iran denies seeking or ever having sought to build the atomic bomb while steadily expanding its nuclear programme over the years in defiance of multiple UN Security Council resolutions and sanctions.
Some experts warn that Iran may next year reach "critical capacity" -- the point at which it could, in theory, process sufficient weapons-grade uranium for a bomb before being detected.
Since taking office in August, President Hassan Rouhani, seen as a relative moderate, has however raised hopes that the long-running crisis can be resolved.
Iran's Foreign Minister Javad Zarif held a landmark meeting with US Secretary of State John Kerry during the UN General Assembly in September, and US President Barack Obama and Rouhani also shared a historic phone call.
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Then in Geneva on October 15-16, Iran presented to the P5+1 a new proposal that Araqchi said could settle the dispute "within a year".
But after many false dawns in the long-running standoff, it remains to be seen whether a deal that satisfies both sides is possible.
Watching the talks closely will be Israel, which is widely believed to have its own nuclear arsenal and has refused to rule out bombing its arch-rival.
Close tabs on nuclear work
The IAEA regularly inspects Iran's nuclear activities, and Western countries want any accord to include Tehran allowing the watchdog to keep a closer eye on its activities.
This would enable the IAEA to better detect any attempt by Iran to "break out" and produce highly enriched uranium for an atomic bomb, and to inspect suspected secret nuclear sites.
But Monday's talks are mainly focused on the past: allegations that before 2003, and possibly since, Iran conducted research work into making a nuclear weapon.
For almost two years, since the IAEA published a major report on these allegations in November 2011, Iran has resisted pressure to allow the agency to probe the claims.
Iran says they are based on faulty CIA and Mossad intelligence that it complains it has not been allowed to see.
But Mark Hibbs, analyst at the Carnegie Foundation for International Peace, says that Iran cooperating with the IAEA would "add confidence and momentum" to the Geneva talks.
"Until now a lack of agreement between the IAEA and Iran has been an obstacle in negotiations between Iran and the P5+1," Hibbs told AFP.