'MEASURABLE PROGRESS'

The report said: "The elimination of the chemical weapons programme of the Syrian Arab Republic stands at a critical juncture."

"While progress has been attained under challenging circumstances, it is clear the Syrian Arab Republic must further intensify and accelerate its efforts towards the full elimination of its chemical weapons programme," it said.

Under the OPCW schedule, all Syria's declared chemical weapons must be destroyed by June 30. Most of the chemicals are supposed to be transported to the port of Latakia, where they will be shipped out of the country.

The United States has sent the MV Cape Ray, a ship outfitted with special equipment to neutralize the worst of Syria's chemicals at sea, and says it will need 90 days to complete the destruction.

"Measurable progress has been made over the last months in the destruction of critical equipment and special features at a number of chemical weapons production facilities, as well as unfilled chemical munitions," the report said. "As a result, the production, mixing and filling capabilities of the Syrian Arab Republic have been rendered inoperable."

The deal for Syria to give up its chemical weapons, brokered by the United States and Russia, was enshrined in a UN Security Council resolution in September.

The resolution does not authorize automatic punitive action in the form of military strikes or sanctions if Syria does not comply. At Russia's insistence, the resolution makes clear a second council decision would be needed for that.

Russia has made clear, however, it would not support the use of force against Assad's government, a close ally.