That step will ensure that Syria can no longer make new chemical weapons. After that, the international community and Syria have to agree to a plan to destroy the country's chemical stockpile.
Syria is believed to possess around 1,000 metric tons of chemical weapons, including mustard gas and the nerve agent sarin. It has sent the OPCW a plan for full destruction of the stockpile that has to be discussed by the group's executive council next month.
The OPCW, based in The Hague, said such declarations by member states "provide the basis on which plans are devised for a systematic, total and verified destruction of declared chemical weapons and production facilities".
State Department spokeswoman Jen Psaki said Monday that Washington was reviewing the declaration, which ran to more than 700 pages. "We are, in accordance with OPCW regulations, not going to publicly discuss or analyse our assessment of the report," she said.
The two sites the inspectors still need to check appear to be in rebel-held or contested areas. At least one of the locations is believed to be the town of al-Safira, which experts say is home to a production facility as well as storage sites. The area has been engulfed by fighting for months, and many of the rebels in the area are from al-Qaeda-linked groups.
The OPCW-UN mission stems from a deadly chemical attack on rebel-held suburbs of Damascus in August that killed hundreds. Assad denied any role in the attack, while the US and its allies blamed his government and threatened to carry out punitive missile strikes.
The US and Russia then brokered an agreement for Syria to relinquish its chemical arsenal. Assad quickly agreed, and the deal was enshrined in a UN Security Council resolution.
That resolution also endorsed a roadmap for a political transition in Syria, and called for a peace conference to be held in Geneva as soon as possible. Diplomatic efforts to convene the meeting have sputtered, however, amid disagreements over the agenda and participants.
UN-Arab League envoy Lakhdar Brahimi traveled to Damascus Monday as part of his regional trip to try to drum up support for the conference. Brahimi is expected to meet Syrian officials as well as members of local opposition groups. It is not clear whether he will meet Assad, who was furious with the envoy after Brahimi said in December that the Assad family's 40-year rule of Syria was "too long".
Also Monday, Syrian government forces retook a Christian town north of Damascus, expelling al-Qaeda-linked rebels after a week of heavy fighting, state media and opposition activists said.
The state-run SANA news agency said the army "restored security and stability" to the town of Sadad, 120 kilometres north of Damascus, and that "a large number of terrorists" were killed.
The Britain-based Syrian Observatory for Human Rights said the government had retaken the town but that rebels had successfully withdrawn.
SANA also said that rebel fighters captured a member of parliament, Sheik Mahna el-Fayadh, on Sunday near the eastern city of Deir el-Zour. The Observatory said el-Fayadh was being held by rebels from the Ahrar al-Sham brigade as well as the al-Qaeda-linked Islamic State in Iraq and the Levant.
- AP