Washington - The United States has identified three sites in Syria as possible locations of secret nuclear facilities, the Washington Post reported Thursday.

Unidentified US officials told the Post that the US wanted to know if the sites served as support facilities for the alleged al-Kibar nuclear reactor that was destroyed by an Israeli air attack in September.

The report said the US was pushing the UN nuclear watchdog, the International Atomic Energy Agency, to expand its inspections to the three sites.

In a separate development, White House National Security Advisor Stephen Hadley told a high-level meeting on weapons proliferation in Washington Wednesday that ballistic missile testing components were stopped on their way to Syria last year in a four-country coordinated effort.

Hadley revealed the findings at the fifth anniversary meeting of the Proliferation Security Initiative (PSI), the joint effort of some 90 countries to interdict the sale and shipment of weapons of mass destruction to illicit recipient countries or groups.

Hadley hailed the deflection of delivery of the equipment to Syria in February 2007 as an example of the success of the PSI efforts.

Without naming the countries, he said "four nations represented in this room" worked together to stop the shipment.

"A firm in one nation had manufactured the equipment. A firm in another nation was the intermediary that sold it to Syria. The shipping company was flagged in a third nation. And customs officials at the port of a fourth nation were alerted to offload and inspect the equipment and send it back to the country of origin," Hadley said.

The incident had not been widely reported. Hadley said however it was just one of "many shipments of sensitive materials destined for Iran, North Korea and Syria" that had been stopped.

Last month, the IAEA said it intended to investigate the information about Syria's al-Kibar site that was bombed by Israel, and the Post reported that the watchdog agency is negotiating for admission to Syria.

At the time, the IAEA was critical of the US and Israel for withholding information it had about Syria's alleged nuclear power plant and its connection to North Korea.

The US first revealed its suspicions in April, nearly eight months after the attack, that Pyongyang helped Syria build the reactor.

The US charged that Syria had broken its international obligations by hiding the facility from the IAEA. (dpa)