Iran and Syria found themselves in the spotlight Monday as the UN nuclear watchdog convened for its traditional week-long spring meeting.

The International Atomic Energy Agengy's 35-member board of governors was set to discuss two new reports showing little or no progress in the watchdog's long-running investigations into Iran's controversial atomic programme and allegations of illicit nuclear activity on the part of Syria.

In his opening address to the closed-door session, IAEA director general Yukiya Amano complained that Iran was "not providing the necessary cooperation" and that Syria "has not cooperated with the agency since June 2008."

Just 10 days ago, Amano circulated to member states updated reports which said that inspectors had received "new information" about possible military dimensions to Tehran's programme, but made scant progress in their probe against Damascus.

In the run-up to this week's meeting, diplomats had suggested that some member states might seek to table resolutions against both Iran and Syria, as a way of turning up the pressure on the two governments.

But with world attention currently focussed on unrest in the Arab world, and western countries undecided about how much pressure to apply, diplomats said any possible action against Tehran and Syria would now probably be set back until the next board meeting in June.

The IAEA has been investigating Iran's nuclear programme for eight years now, but has so far been unable to establish whether it is entirely peaceful as Iran claims or masks a covert drive to build a bomb as western powers believe.

Iran is continuing to defy UN orders to halt uranium enrichment, the most controversial part of its nuclear drive, because enriched uranium can be used not only to make nuclear fuel, but also the fissile material for a bomb.

In fact, the IAEA said Iran's stockpile of low-enriched uranium in the main branch of its Natanz uranium enrichment plant had now reached 3,606 kilogrammes (7,933 pounds).

Among the many unresolved issues about Iran's atomic drive are allegations that Iran was involved in weaponisation studies -- work which included uranium conversion, high explosives testing and the adaptation of a ballistic missile cone to carry a nuclear warhead -- at least until 2003.

Iran has dismissed the evidence as "fabricated" and refused to discuss the so-called "alleged studies" any further.

Nevertheless, "additional information... has come to the (agency's) attention since August 2008, including new information recently received" that prompted "further concerns," Amano wrote in his latest 12-page report.

In his opening speech on Monday, the Japanese diplomat said: "Iran is not providing the necessary cooperation to enable the Agency to provide credible assurance about the absence of undeclared nuclear material and activities in Iran, and therefore to conclude that all nuclear material in Iran is in peaceful activities."

And he urged Iran "to take steps towards the full implementation of its Safeguards Agreement and its other obligations."

In his separate report on Syria, Amano complained that Damascus was still refusing to cooperate on allegations that it had been building an undeclared nuclear reactor at a remote desert site called Dair Alzour until it was destroyed by Israeli planes in September 2007.

Syria granted UN inspectors one-off access to the site in June 2008 but no follow-up visits to either Dair Alzour or other possible related sites since then.

In a sign of his growing impatience with Damascus, Amano sent a letter to Syria's foreign ministry on November 18 asking the government to provide the IAEA with prompt access to relevant information and locations" connected to Dair Alzour.

In response, Damascus has agreed to a new visit by IAEA inspectors, not of Dair Alzour, however, but of a less significant site at Homs in the west of the country, which is not one of the sites viewed as suspect by inspectors.

The visit will take place on April 1. And in his address to the board of governors, Amano said a pledge by Syria that it would cooperate with the IAEA on "oustanding technical issues ... could represent a step forward."