The United States said on Wednesday that United Nations inspectors had found growing evidence of covert nuclear activity in Syria, and European allies said a lack of Syrian transparency demanded utmost scrutiny.
The UN nuclear watchdog, the International Atomic Energy Agency, is looking into U.S. intelligence reports that Syria had almost built a North Korean-designed, nuclear reactor meant to yield bomb-grade plutonium before Israel bombed it in 2007.
Last month, the IAEA said inspectors had found enough traces of uranium in soil samples taken in a trip to the bombed site granted by Syria last June to constitute a "significant" find, and satellite pictures taken before the Israeli bombing revealed a building resembling a reactor.
But the IAEA report said Syria, citing national security reasons, had ignored many agency requests for further on-the-ground access and documentation to back up its assertion that Israel's target was a purely conventional military building.
"This report contributes to the growing evidence of clandestine nuclear activities in Syria," Gregory Schulte, U.S. ambassador to the IAEA, said during a debate by its 35-nation Board of Governors in Vienna.
"We must understand why such [uranium] material - material not previously declared to the IAEA - existed in Syria and this can only happen if Syria provides the cooperation requested."
He said it was also essential that Syria allow inspectors to examine debris removed from the bombed facility to an unknown location immediately after Israel's strike.
This applied as well, Schulte said, to three other military sites which satellite pictures showed Syria "sanitized" - landscaping them and whisking away equipment - shortly after the IAEA asked to check them out.
Last week, Damascus said the uranium particles were not "significant". It said they came from depleted uranium used in Israeli munitions, contradicting an IAEA finding that this was chemically processed uranium not in Syria's declared inventory.
Syria also suggested IAEA analyses were faulty and that satellite imagery Washington gave to the IAEA was fabricated. Its only declared nuclear site is an old research reactor, and it has no known nuclear energy capacity.
In a statement to the closed-door IAEA gathering, the 27-member European Union voiced concern at the "possibility that Syria has not declared all its nuclear installations".
"Any obstacles, unnecessary delays or a lack of cooperation... undermine the credibility of the agency's verification capabilities. Such cases, therefore, deserve our utmost attention," it said."
Vienna diplomats said Syria had told the IAEA it had built a missile facility on the desert tract hit by Israel, a disclosure apparently meant to reinforce the Syrian refusal to grant more IAEA access on national security grounds.