UN atomic watchdog chief Yukiya Amano turned up the heat on Syria and Iran -- both accused of illicit nuclear activity -- as the body's policy-making board of governors began meeting here Monday.

Tehran and Damascus are both accused of actively blocking the International Atomic Energy Agency's long-running investigations into illegal nuclear activity.

At the end of May, Amano released two new reports in which he said Iran was continuing to stockpile low-enriched uranium, in defiance of multiple UN sanctions, and refusing to answer allegations of possible military dimensions to its contested nuclear programme.

Syria, for its part, is accused of building an undeclared atomic reactor at a remote desert site and has not allowed UN inspectors access to locations, data or individuals who could help clear up the allegations.

Addressing the IAEA's governors on the first day of their traditional week-long June meeting, Amano defended his decision to go public with his assessment that a suspect site in Syria was "very likely" to have been an undeclared nuclear reactor, as alleged by the United States.

"The Syrian government was given ample time by the agency to cooperate fully concerning the Dair Alzour site, but did not do so," Amano said, according to a copy of his speech circulated to journalists.

"Nevertheless, we had obtained enough information to draw a conclusion. I judged it appropriate to inform member states of our conclusion at this stage as it was in no one's interest to let this situation drag on indefinitely," Amano said.

Damascus has always insisted that Dair Alzour was a non-nuclear military installation, but has provided no evidence to back that up. Furthermore, it has repeatedly denied the IAEA access to the site to clear up the allegations for itself.

"I am confident about our conclusion and I look forward to engaging further with Syria to resolve related outstanding issues," Amano said.

He told a news conference later that, a couple of days after his report, Syria wrote to the IAEA promising full cooperation and that officials from both sides had since met for talks.

"But expressing an intention is not good enough. We would like to see concrete results," Amano said.

Syria had still not provided any concrete indication as to what form its full cooperation would take. Nevertheless, the two sides had agreed to meet again following the end of the June session of the board of governors, Amano continued.

The US and its Western allies are expected to propose a resolution at the board meeting to find Damascus in "non-compliance with its international obligations and report it to the UN Security Council in New York.

Western diplomats believe there is sufficient support on the 35-member board for the resolution to be passed, although it would be "naive" to expect it to be carried unanimously, a number of them said.

Asked if a resolution would jeopardise Damascus's willingness to cooperate, Amano replied: "Whether to report it to Security Council or not is the matter of member states, I'm not involved in that."

But even if Damascus were to be reported to New York, "I don't think it changes my work. What is needed... is that Syria is prepared to cooperate with us and I'm looking forward to work with them whatever happens."

The last time a member state was reported to the UN Security Council was Iran in February 2006 and the IAEA is still no closer than it was then to establishing whether the Islamic republic's nuclear programme is exclusively peaceful, as Tehran maintains.

Turning to the IAEA's long-running Iran investigation, Amano said the watchdog "has received further information related to possible past or current undisclosed nuclear-related activities that seem to point to the existence of possible military dimensions to Iran's nuclear programme."

The IAEA has long been pressing Tehran to answer the allegations. But Iran has merely dismissed the evidence backing up the allegations as "fabricated" and "baseless", and refused to discuss the matter further.