The United Nations nuclear watchdog began an investigation into an alleged Syrian reactor bombed by Israel.
A team from the International Atomic Energy Agency flew out to Damascus on Sunday for 72 hours of talks and inspections.
The experts are to visit al-Kibar, a remote site in northern Syria which Israeli warplanes destroyed last September and which the United States has described as a North Korean-designed reactor.
Syria has denied having a secret nuclear facility but, in a move widely perceived as aimed at covering up evidence, bulldozed over al-Kibar soon after the Israeli attack.
Damascus admitted the IAEA inspectors after months of prevarication. There have been calls abroad for several other suspect sites in Syria to be inspected, but the IAEA is for now only being granted access to al-Kibar.