The head of the mission charged with destroying Syria's chemical weapons says preparations are on track to move the most dangerous chemical agents from sites in the war-torn country to the port of Latakia but there are serious security issues on key roads.

Sigrid Kaag told reporters after briefing the U.N. Security Council Wednesday "there are factors beyond our control" that could affect the ambitious schedule to destroy Syria's entire chemical weapons program by mid-2014.

As an example, she said, bad security on the road connecting Damascus and the northern city of Homs, a key artery en route to Latakia, forced her to fly to Beirut and then to Latakia by helicopter for a meeting in recent days.

Kaag says if that road can't be used, "it's a real issue."