Syria has dismissed allegations of a secret nuclear programme
The head of Syria's nuclear programme has said that the country's military sites will remain off-limits to international nuclear inspectors.
Damascus said it would co-operate with an International Atomic Energy Agency (IAEA) inquiry only if it did not threaten its national security.
The watchdog is investigating claims of a secret Syrian nuclear programme.
Syria's announcement comes after it dropped a bid to win a place on the board of the IAEA.
The IAEA investigation follows US allegations that Damascus was close to completing a nuclear reactor at a secret location, which was bombed by Israel last year.
Syria has denied the allegations as "ridiculous".
Ibrahim Othman told the IAEA that his government was "co-operating with the agency in full transparency".
"However, this co-operation will not be in any way at the expense of disclosing our military sites or causing a threat to our national security," he added.
Damascus allowed IAEA inspectors to visit the site at al-Kibar in June but has refused any follow-up trips.
On Friday, Syria dropped its bid for a place on the IAEA board, leaving the post open to Western-backed Afghanistan.
Both had been vying for the same seat on the board, representing the Middle East and South Asia (Mesa) group.
The body had been facing a divisive and unprecedented vote on the issue.
IAEA Director Mohamed ElBaradei said Syria's co-operation had been "good", but it needed to show "maximum co-operation" for the agency to draw any conclusions.
A Syrian officer reported to have been in charge of facilitating the IAEA probe was killed in unexplained circumstances last summer, further delaying the proceedings.
On Wednesday Iran, also accused by some countries of clandestine nuclear activity, dropped its bid for a seat on the IAEA board, saying it wanted to make way for regional ally Syria to join instead.