Welcoming the move following talks in Tehran, IAEA chief Mohamed ElBaradei said an explanation from Iran should be forthcoming by the end of May.

"This in my view is a positive step. I hope they will be able to clarify within a few weeks this important issue," ElBaradei told journalists on a visit to Sarajevo.

"It is my understanding that hopefully by the end of May we will be in a position to get an explanation and clarification from Iran as to these alleged studies," ElBaradei said.

"An agreement was reached during the meetings in Tehran on a process that aims to clarify the so-called alleged studies during the month of May," IAEA spokeswoman Melissa Fleming said in a statement issued earlier in Vienna.

IAEA deputy director general Olli Heinonen held closed-door talks with Iranian officials in Tehran Monday and Tuesday but no information filtered out on the contents of the discussions amid an apparent media blackout.

The aim of the two-day visit was to press Iran over claims it has carried out alleged "weaponisation studies", the Vienna-based watchdog said earlier.

In a closed-door briefing to diplomats at IAEA headquarters in Vienna on February 25, Heinonen presented detailed evidence suggesting that Iran could have been studying how to use its nuclear technology to make a warhead.

Western diplomats present at the meeting subsequently said the new evidence of alleged "weaponisation studies" was troubling.

Iran, which insists its nuclear programme is entirely peaceful and aimed solely at generating energy, at the time furiously denounced the claims as fake.

Iran's refusal to suspend sensitive uranium enrichment operations -- which the West fears could be used to make a nuclear weapon -- has already led to three sets of UN Security Council sanctions against Tehran.

Despite more than four years of intensive investigation, the IAEA has never been able to confirm the nuclear drive is peaceful and bring its probe to a conclusion.

Commenting on the talks with Heinonen, an unnamed spokesman of the Iranian delegation told the IRNA news agency, "Iran, as announced before, will continue cooperation with the agency within the regulations of this international body.

"Iran's doors for talks with the legal representatives of the agency are open and Iran will continue cooperation with the agency like before."

No mention was made of the alleged weaponization studies.

Iranian officials have repeatedly played down the links between Heinonen's visit and the alleged studies, insisting his two day trip was for routine talks in the framework of Iran-IAEA cooperation.

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