A tentative deal has been reached with Iran that will allow the UN nuclear agency to restart a long-stalled probe into suspicions that Tehran has secretly worked on developing nuclear arms, the UN nuclear chief said.
The news from International Atomic Energy Agency chief Yukiya Amano comes a day before Iran and six world powers meet in Baghdad for negotiations, and could present a turning point in the dispute over Iran's nuclear intentions.
The six nations - the US, Britain, Russia, China, France and Germany - hope the talks will result in an agreement by Tehran to stop enriching uranium to a higher level that could be turned quickly into the fissile core of nuclear arms.
Iran denies it seeks nuclear weapons and says its reactors are for power and medical applications.
By compromising on the IAEA probe, Iranian negotiators in Baghdad could argue that the onus is on the other side to show some flexibility and temper its demands.
Although Mr Amano's trip and the talks in Baghdad are formally separate, Iran hopes progress with the IAEA can boost its chances in pressing the US and Europe to roll back sanctions that have hit Iran's critical oil exports and blacklisted the country from international banking networks.
It is unclear how far the results achieved by Mr Amano would serve that purpose, with his trip failing to seal a conclusive deal, despite his upbeat comments.
After talks in Tehran with chief Iranian nuclear negotiator Saeed Jalili, Mr Amano said: "The decision was made ... to reach agreement on the mechanics of giving the IAEA access to sites, scientists and documents it seeks to restart its probe."
Mr Amano, speaking to reporters on his return to Vienna airport after his one-day trip to Tehran, said differences existed on "some details", without elaborating, but added that Mr Jalili had assured him that these "will not be an obstacle to reach agreement". He spoke of "an almost clean text" that will be signed soon, although he could not say when.
For the six powers, a main concern is Iran's production of uranium enriched to 20%, which is far higher than needed for regular energy-producing reactors but used for one Iran says it needs for medical research. The US and its allies fear the higher-enriched uranium could be quickly boosted to warhead-grade material.