By Fredrik Dahl
VIENNA (Reuters) - With international attention focused on Syria's tentative offer to give up its chemical arsenal, the United States and Israel used a U.N. nuclear agency meeting to press Damascus to also open up to an inquiry into its atomic activities.
Though not seen as cause for immediate alarm like Syria's poison gas stocks, Damascus' continuing failure to cooperate with U.N. nuclear inspectors was singled out by U.S. and Israeli envoys at the closed-door session of the agency's board of governors in Vienna, diplomats said.
The International Atomic Energy Agency has long sought to visit a Syrian desert site U.S. intelligence reports say was a nascent, North Korean-designed reactor geared to making plutonium for nuclear bombs - before Israel bombed it in 2007.
"Syria is as much trustworthy in the nuclear domain as it is in the chemical domain," Israeli Ambassador Ehud Azoulay told the IAEA's 35-nation board on Thursday, according to a copy of his speech made available to Reuters after the meeting.
A senior U.S. diplomat said Syria - ravaged by a civil war that has killed more than 100,000 people since 2011 - must grant the IAEA access to all relevant locations, materials and persons for its five-year-old inquiry.
"Until the agency is able to resolve all outstanding questions about the exclusively peaceful nature of Syria's nuclear program, Syria's non-compliance will remain a matter of serious concern," U.S. Ambassador Joseph Macmanus added.
Syria's envoy to the IAEA was not available for comment.
Syria has said the site at Deir al-Zor in eastern Syria was a conventional military base but the IAEA concluded in 2011 that it was "very likely" to have been a reactor that should have been declared to its anti-proliferation inspectors.
IAEA inspectors examined the site in June 2008 but Syrian authorities have barred them access since. In February, opposition sources in eastern Syria said rebels had captured the destroyed site near the Euphrates River.
The IAEA has also been requesting information about three other sites that may have been linked to Deir al-Zor.
IAEA Director General Yukiya Amano told the board that his agency remained "unable to provide any assessment concerning the nature, or operational status" of those locations.
A U.S. think-tank, the Institute for Science and International Security (ISIS), said Syria was not believed to have an active, secret nuclear program now.
"But Syria is believed to be actively hiding assets associated with this past, undeclared nuclear reactor effort," it said in a report published late on Thursday.
Israel is widely assumed to be the Middle East's only nuclear-armed power, drawing Arab and Iranian condemnation.
The Jewish state and Washington see Iran's disputed nuclear program - and to a lesser extent Syria's possible activities - as the volatile region's main proliferation concern. Tehran says its program is an entirely peaceful energy project.
Iran's envoy to the IAEA, Reza Najafi, accused Israel during this week's board discussion on Tehran's nuclear program of trying to "divert the attention from its clandestine nuclear weapons program by making unsubstantiated allegations".
Western and Israeli security experts earlier this year said they suspected that Syria may have tons of unenriched uranium in storage and that any such stockpile could potentially be of interest to its ally Iran.
Even if Syria did have such a stockpile, it would not be usable for nuclear weapons in its present form, a fact that makes it less of a pressing concern for the West than government forces' alleged use of chemical weapons against their foes.
"Any known or suspected nuclear materials inside Syria are not nearly as dangerous as Syria's chemical weapons stockpile ... since the nuclear material in this case cannot be used directly to make nuclear weapons," ISIS said.
Nonetheless, a large stock of natural uranium metal would pose nuclear proliferation risks as it could be obtained by militant groups or countries like Iran, the think-tank said.
The Syrian government has offered to join a global pact banning chemical weapons to head off the risk of punitive U.S. air strikes over an August 21 poison gas attack that killed hundreds of civilians in a rebel district.
(Editing by Mark Heinrich)