At issue are the so-called "alleged studies" handed over to the International Atomic Energy Agency (IAEA), suggesting discrepancies in Tehran's declared programme and possible weaponisation work.

"A team led by Olli Heinonen will travel to Tehran early next week for meetings with Iranian officials about the 'alleged studies'," said IAEA spokeswoman, Melissa Fleming.

The so-called alleged studies are the one outstanding issue that the IAEA insists still needs to be cleared up.

The studies include: charts on a uranium conversion process different from Iran's declared activities; a document on the casting and machining of uranium metal into the shape of warheads; schematics of a Shahab-3 missile re-entry vehicle that in the opinion of the IAEA "is quite likely to be able to accommodate a nuclear device"; and remote explosives testing, including plans for underground detonations facilities and a separate firing facility 10 kilometres (six miles) away.

Tehran has repeatedly dismissed the allegations as baseless and the intelligence used to back them up as fake.

But in a closed-door briefing to diplomats at IAEA headquarters in Vienna on February 25, Heinonen presented detailed evidence from member states 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 was troubling.

According to a report earlier Friday by the Iranian student news agency ISNA, Heinonen would be accompanied by the IAEA's director for safeguards operations Herman Nackaerts on a two-day trip.

INSA also quoted an unnamed official at Iran's atomic energy organisation was quoted as saying the talks would focus on "alleged studies".

"Since there is a difference of opinion between Iran and the agency over the examination of the purported studies, the Monday talks will be focused only on reaching a solution for examining this issue," the official was quoted as saying.

Tehran insists its nuclear programme is entirely peaceful and aimed solely at generating energy but the West fears Iran could be seeking an atomic weapon.

Iran's Deputy National Security Chief Javad Vaeedi, its Ambassador to the IAEA, Ali Asghar Soltanieh, and the Deputy Head of its Atomic Energy organisation, Mohammad Saeedi, will meet Heinonen, the official told ISNA.

Iran has repeatedly said that it considers its nuclear case closed after it answered the UN watchdog's questions about the history of its nuclear drive.

The IAEA, however, has said it is still unable to confirm the nature of Iran's nuclear programme and complained that Tehran has defied repeated UN Security Council ultimatums to suspend uranium enrichment.

Enrichment can be used to develop an atomic bomb as well as produce nuclear fuel. Iran has been slapped with three sets of UN sanctions over its refusal to suspend the process.

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