Syria has missed the first of a series of tight deadlines for the destruction or removal of its chemical weapons stockpile by mid-2014.
United Nations inspectors have been unable to visit two of the 23 sites declared by Syria before the agreed date of October 27.
Ceasefires between rebels and forces loyal to President Bashir al-Assad may be required to complete the inspection.
Syria has listed 1,000 tonnes of chemical weapons and another 290 tonnes of toxic or chemical agents along with 1230 unfilled chemical munitions.
By another deadline of next Friday Damascus must have rendered unusable all production and chemical weapons filing facilities.
Syria agreed to destroy its chemical arsenal under a Russian-American brokered deal, which avoided threatened force from the US.But the targets are ambitious as the destruction of the weapons is a complex process many experts claim could take years.