* OPCW says inspected 21 of 23 chemical weapons sites
* Met deadline of Nov. 1 to destroy production facilities
* By mid-2014 must have destroyed all chemical weapons
* Agreement to destroy follows deadly Aug 21 sarin attack
BEIRUT, Oct 31 (Reuters) - Syria has destroyed all of its declared chemical weapons production and mixing facilities, meeting a major deadline in an ambitious disarmament programme, the international chemical weapons watchdog said in a document seen by Reuters.
The Organisation for the Prohibition of Chemical Weapons said its teams had inspected 21 out of 23 chemical weapons sites across the country. The other two were too dangerous to inspect, but the chemical equipment had already been moved to other sites that experts had visited, it said.
"The OPCW is satisfied it has verified, and seen destroyed, all declared critical production/mixing/filling equipment from all 23 sites," the document said.
Under a Russian-American brokered deal, Damascus agreed to destroy all its chemical weapons after Washington threatened to use force in response to the killing of hundreds of people in a sarin attack on the outskirts of Damascus on Aug. 21.
It was the world's deadliest chemical weapons incident since Saddam Hussein's forces used poison gas against the Kurdish town of Halabja 25 years ago.
The United States and its allies blamed Assad's forces for the attack and several earlier incidents. The Syrian president has rejected the charge, blaming rebel brigades.
Under the disarmament timetable, Syria was due to render unusable all production and chemical weapons filling facilities by Nov. 1 - a target it has now met. By mid-2014 it must have destroyed its entire stockpile of chemical weapons.
The OPCW mission is being undertaken in the midst of Syria's 2-1/2 year civil war, which has killed more than 100,000 people. The unprecedented conditions had raised concerns that the violence would impede the disarmament, but the OPCW says Syrian authorities have been cooperating with the weapons experts, who have been able to visit all but three of the chemical sites.
At one of those locations the OPCW said it was able to verify destruction work remotely, while Syrian forces had abandoned the other two sites.
Syrian authorities said that "the chemical weapons programme items removed from these sites were moved to other declared sites," the document said. "These sites holding items from abandoned facilities were inspected."
The OPCW has not said which sites it has been unable to visit, but a source briefed on their operations said one of them was in the Aleppo area of northern Syria and another was in Damascus province.
One major chemical weapons site is located close to the town of Safira, south-east of Aleppo. Assad's forces have bombarded the town in recent weeks in an attempt to expel rebel fighters including al Qaeda-linked brigades.