Syria has snubbed a request by UN atomic watchdog chief Yukiya Amano for prompt access to a suspect nuclear site and a number of other locations, diplomats said on Tuesday.

After more than two years of deadlock on the issue, Syria could therefore find itself under intensified scrutiny at a meeting of the 35-member board of governors of the Viennna-based International Atomic Energy Agency next month.

A number of countries could start even pushing for a possible resolution against Damascus or perhaps table the idea of a so-called "special inspection", a rarely-used tool that allows UN inspectors to request more intrusive access to sites, the diplomats told AFP, speaking on condition of anonymity.

And if Syria were to block that request, it could face possible referral to the UN Security Council.

The IAEA has been investigating allegations since 2008 that Syria had been building an undeclared reactor at a remote desert site called Dair Alzour until it was bombed by Israeli planes in September 2007.

Damascus 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.

On the basis of that one visit, the IAEA has already said the building bore some of the characteristics of a nuclear facility.

UN inspectors also detected "significant" traces of man-made uranium there, as yet unexplained by Damascus.

In what diplomats saw at the time as a sign of Amano's growing impatience, the watchdog chief 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 an alleged nuclear site.

Amano himself described it as the first time that an IAEA director general had contacted the Syrian government directly with regard to the agency's probe.

Nevertheless, Syria "has failed so far to come up with any of the information or access that Amano was looking for," one western diplomat said.

The United States, in particular, could be among those pushing for a special inspection.

On December 2, a number of US lawmakers wrote to President Barack Obama askimg him to press the IAEA for such a move.

But some diplomats here caution against using such a tool at this stage.

The last time the IAEA resorted to such a measure was in North Korea in 1993. Pyongyang defied the request and subsequently went on to develop a nuclear weapon capacity.

"So, the question here is what action could the IAEA could take if Syria similarly refused," one diplomat said.

The IAEA board of governors is scheduled to convene for its traditional spring meeting from March 7-11, where, alongside the Syrian issue, the long-running probe into Iran's controversial nuclear programme will once again dominate discussions.