The organization said inspectors would finish destroying equipment used to mix chemicals and fill weapons by the beginning of November, a benchmark in the process of cataloging and destroying Syria's chemical weapons arsenal, The New York Times reported Tuesday.
"The two remaining sites have not been visited due to security reasons," the Organization for the Prohibition of Chemical Weapons said Monday in a statement. "Efforts by the joint mission to ensure the conditions necessary for safe access to those sites will continue."
The two sites the inspectors haven't visited are in "contested areas where you need some kind of cease-fire or guarantees for the safety of the inspectors," OPCW spokesman Michael Luhan told the Times.
It wasn't clear where the sites are or who controls the area. Responsibility for the inspectors' security and negotiating access to sites is with the United Nations.
A senior U.S. State Department official said Monday the disarmament process was generally on track and there "was reason to be optimistic," despite the setback.
The official told the Times the Syrian government submitted a plan to purge its chemical weapons stockpile that would allow for the elimination of precursor chemicals used to make poison gas so they could be destroyed outside Syria.
Norway rejected a U.S. request to locate equipment there to help destroy Syria's chemical arsenal.
The State Department official was confident other nations would agree to offer destruction sites, the Times said. The United States isn't among the possible sites because Syrian officials said they don't want to turn their chemical weapons over to the United States, the official said.
Syria's declaration of its chemical arsenal, submitted last week, is 714 pages long, a European diplomat said.
Although Syria disclosed 23 sites, U.S. officials said in September they believed there are at least at least 45 sites.
The European diplomat, who saw relevant documents, said Syria now is reporting 41 chemical weapons facilities at the 23 sites it disclosed, which may explain the discrepancy and close the gap between Syria's disclosure and the figure stated by U.S. officials, the Times reported.
The OPCW executive council likely will discuss Syria's declaration next week and is expected to give its decision on the Syrian plan by mid-November, the Times said.