A Syrian site reportedly bombed by Israel in 2007 was "very likely" to have been a nuclear reactor, the UN atomic agency said in a report that could pave the way for Damascus to be referred to the UN Security Council next month.

The confidential report by the International Atomic Energy Agency (IAEA) threw independent weight behind U.S. allegations that Syria was secretly building a reactor at the Dair Alzour site in the desert, possibly with military aims.

Open gallery view Syria nuclear facility Credit: Reuters / Archive

It was obtained by Reuters on Tuesday, a day after the European Union imposed sanctions on Syrian President Bashar Assad and other senior officials, raising pressure on his government to end weeks of violence against protesters.

Syrian activists say more than 1,000 civilians have been killed in a crackdown on demonstrators opposing Assad's rule.

The West has become increasingly frustrated over what is seen as Syria's stonewalling of an IAEA probe into Dair Alzour, which U.S. intelligence reports said was a nascent North Korean-designed reactor intended to make bomb fuel.

Syria, an ally of Iran, denies harboring a nuclear weapons program and says the IAEA should focus on Israel instead because of its undeclared nuclear arsenal.

" ... the agency assesses that it was very likely that the building destroyed at Dair Alzour site was a nuclear reactor which should have been declared to the agency," the IAEA said.

The report suggested it may have been a gas-cooled graphite moderated reactor -- a model found also in North Korea, whose nuclear weapons ambitions have drawn punitive UN measures.

The Vienna-based UN body had previously said there were indications nuclear activity may have taken place at the site.

The United States and its European allies are expected to seize on the report's finding to push for a decision by the IAEA's 35-nation board, meeting on June 6-10, to report the Syrian nuclear issue to the UN Security Council.

Syria under pressure

"The report provides the IAEA's conclusion that Syria was constructing a covert nuclear reactor, and we believe that reactor was designed to produce plutonium for possible use in nuclear weapons," a Western diplomat said.

But some non-Western envoys have expressed skepticism about any such step by the IAEA board, saying that whatever Syria did at Dair Alzour it was now in the past.

The board has the power to refer countries to the Security Council if they are judged to have violated IAEA rules -- designed to make sure atom technology is not diverted for military aims -- by carrying out secret nuclear work.

It reported Iran to the Security Council in 2006 over its failure to dispel suspicions that it was trying to develop nuclear weapons. Tehran has since been hit with four rounds of UN sanctions over its refusal to curb sensitive nuclear work.

Saying Dair Alzour was a military, non-nuclear site, Syria has for nearly three years refused to allow UN inspectors to revisit the site, after a one-off inspection in 2008.

"The agency regrets that Syria has not cooperated since June 2008 in connection with the unresolved issues related to the Dair Alzour site," the IAEA report said.

Western diplomats say Syria's rejections of repeated requests for follow-up access risk undermining the IAEA and the nuclear Non-Proliferation Treaty that underpins its work to prevent the spread of atom bombs, if nothing is done.

"It was a long time coming but I think it is a positive step," Paul Brannan, a senior analyst of the Washington-based Institute for Science and International Security (ISIS), said about the IAEA's report.

