The UN atomic watchdog convened Monday to discuss the latest developments in its long-running probes of disputed nuclear drives in Iran and Syria, with chief Yukiya Amano set to address the closed-door assembly.

The 35-member board of the International Atomic Energy Agency faces a packed agenda at its traditional September meeting this week.

The topics range from nuclear security and the IAEA's two-yearly programme performance report, as well as the appointment of a number of deputy directors general, including the successor to the IAEA's top inspector Olli Heinonen, who resigned last month.

The board meeting also acts as a prelude to the agency's annual general conference -- which brings together all 151 member states -- next week.

Nevertheless, diplomats said it was the IAEA's latest reports on Iran and Syria, circulated to member states last week, that would likely be the focus of attention, as would be any remarks made by Director General Yukiya Amano on the two dossiers in his opening address.

The Iran report complained that the Islamic republic was hampering the agency's work by barring experienced inspectors.

It found that Tehran was continuing to increase its stockpile of both low-enriched and higher-enriched uranium in defiance of UN orders to halt any such activity until the IAEA can determine the true nature of Tehran's nuclear programme.

It said that Iran was still refusing to answer questions about possible military dimensions to its work.

And although the head of Tehran's atomic agency Ali Akhbar Salehi boasted last month that sites had been chosen for 10 new uranium enrichment facilities, Iran has not provided the agency with any information about those sites, as it is obliged to do under its safeguards agreement.

Last week, Iranian opposition group the National Council of Resistance of Iran (NCRI) claimed Iran was building a new uranium enrichment site in Abyek, about 120 kilometres (70 miles) northwest of Tehran.

But Iran denied the allegation and experts have also expressed scepticism about the reliability of the information.

Diplomats said they were most troubled by the so-called "de-designation" of inspectors by Iran.

While Tehran is perfectly within its rights to vet IAEA inspectors coming into the country, as every member state is, it is the first time that experienced inspectors who had already been working in a country for a long time had suddenly had their permits revoked.

Diplomats suggest it is a way for Iran to intimidate and dissuade inspectors from asking too many awkward questions.

The IAEA's latest report on Syria showed that Damascus is still stonewalling on a two-year investigation into allegations that it had been building a covert nuclear reactor at a remote desert site with the help of North Korea until it was bombed by Israel in September 2007.

The IAEA could press for a mandatory "special inspection" to resolve the allegations. But diplomats said there was much debate within the agency over whether to resort to such a measure at this stage.

The last time special inspection powers were invoked was in the case of North Korea in 1993. In the end, the hardline communist state still denied the IAEA access and went on to develop a nuclear bomb capacity in secret.