U.N. nuclear watchdog, Iran may meet again in May - source

VIENNA (Reuters) - The U.N. nuclear watchdog and Iran may resume talks next month over a long-stalled investigation into suspected atomic bomb research by the Islamic state, but no date has yet been fixed, a diplomatic source said on Friday.

It would be the 10th round of negotiations between the International Atomic Energy Agency and Iran since the discussions about what the IAEA calls "possible military dimensions" to Tehran's nuclear programme began in early 2012, although disagreements about the scope of IAEA inspections have gone on much longer.

The last session of talks, in February, failed to yield a breakthrough that would enable the IAEA to restart its investigation, and another round in May is a possibility, the source said without elaborating.

The IAEA, whose mission it is to prevent the spread of nuclear weapons in the world, has been trying for more than a year to negotiate a so-called structured approach with Iran that would give it access to sites, officials and documents.

IAEA Director General Yukiya Amano this month said that some of the differences between the two sides were still "quite important". He said any deal with Tehran must enable his inspectors to carry out effective verification work.

In late 2011, the IAEA published a report with a trove of intelligence indicating past research in Iran which could be relevant for nuclear weapons, some of which might still be continuing. Iran dismissed the findings as baseless or forged.

Iran denies Western allegations that it is seeking to develop the capability to build nuclear weapons, saying its atomic activities are aimed at generating electricity.

But its refusal to curb sensitive nuclear work that can have both civilian and military purposes and its lack of openness with IAEA inspectors have drawn increasingly tough Western sanctions targeting its oil exports.

The IAEA-Iran talks are separate from, but still closely linked to, broader diplomatic negotiations between Tehran and six world powers aimed at resolving the decade-old dispute peacefully and prevent a new Middle East war.

Iran and the powers - the United States, France, Germany, Britain, Russia and China - failed to break the deadlock in their last meeting, held this month in Kazakhstan.

Some diplomats and analysts say Iran is merely using the talks with the IAEA for leverage in the separate negotiations with world powers which, unlike the IAEA, have the power to ease sanctions that are hurting its oil-dependent economy.

The IAEA's immediate priority is to visit the Parchin military base. It suspects explosives tests relevant to nuclear weapons may have taken place there, perhaps a decade ago, and then been concealed. Tehran denies the accusation.

(Reporting by Fredrik Dahl)