Syria suggested on Thursday that Israel dropped uranium particles onto Syrian soil from the air to make it look as if a covert nuclear weapons plant was being built there, diplomats at a United Nations nuclear watchdog meeting said.

Damascus has strongly denied U.S. intelligence that a complex in the Syrian desert bombed to ruins by Israel in 2007 had been a nascent nuclear reactor, North Korean in design and geared to making plutonium for atomic bombs.

But International Atomic Energy Agency chief Yukiya Amano last month lent independent support to Western suspicions for the first time by saying uranium traces found in a 2008 visit by inspectors pointed to nuclear-related activity on the ground.

He said Syria was still refusing to let the IAEA re-examine the Dair Alzour site, take swipe samples from rubble removed immediately to an unknown location after the air strike, and check three other sites under military control whose look was altered by landscaping after inspectors asked for access.

In a closed-door debate by the IAEA's 35-nation board of governors, Syria reiterated its assertion that the uranium traces came with munitions Israel used to destroy the complex.

IAEA head inspector Olli Heinonen replied that the chemical composition, size, shape and distribution of the traces made it extremely unlikely they were a type of uranium sometimes used in munitions as a hardening agent, diplomats present said.

Rather, he said, they were traces of processed uranium - which after further treatment could be used for nuclear fuel.

In response, Syrian Ambassador Bassam al-Sabbagh suggested Israel might have contaminated the site with uranium particles dropped by air during or right after the air strike, participants in the meeting told Reuters.

"The IAEA should verify the nature of the material dropped by Israel ... There were planes that overflew the site and we don't know what it was they dropped. I'm not just talking about munitions," Sabbagh was quoted by diplomats as saying.

Western diplomats dismissed his remarks as another twist in Syrian efforts to deflect the IAEA probe without addressing the substance of UN and Western concerns.

"It's part of a pretty weak defense by Syria," said a European Union diplomat, who like others spoke on condition of anonymity.

"I don't think (most delegations) took this seriously," said another diplomat.

Asked about that, a senior UN official familiar with Syria's dossier said: "The best solution would be to let the IAEA take samples from the debris to establish the facts, as the IAEA reports on this have indicated."

Syria denies having atomic bomb aspirations, says the target of Israeli warplanes was a conventional military building and that the intelligence reports were forged.

It is an ally of Iran, which is under a much bigger IAEA investigation over a secretive uranium enrichment program suspected of being geared to yielding nuclear warheads.

The UN watchdog's governors took no action on Syria pending further efforts by inspectors to gain access.

U.S., European and other Western delegates urged Syria to cooperate fully with the IAEA inquiry, while Iran said it was Israel, not Syria, that should be in the agency's dock.

"The core of the problem is an aggressive act committed by the Zionist regime," Iranian Ambassador Ali Asghar Soltanieh said. He blamed Western powers for the IAEA focusing "on the minor issue of a few uranium particles".