"Syria has produced, stored, and weaponized chemical agents, but it remains dependent on foreign suppliers for chemical precursors. The regime of President Bashar al Asad possesses stocks of nerve (sarin, VX) and blister (mustard gas) agents, possibly weaponized into bombs, shells, and missiles. The government also has associated production facilities. Chemical weapons and their agents can deteriorate depending on age and quality; little is known from open sources about the current condition of the stockpile. Syria continues to attempt to procure new supplies of chemical weapons precursors, which are dual-use, through front companies in third countries. Most countries that have had chemical weapons arsenals in the past have destroyed, or are in the process of destroying, these weapons under the Chemical Weapons Convention. The U.S. intelligence community cites Iran, North Korea, and Syria as having active chemical weapons programs. The use or loss of control of chemical weapons stocks in Syria could have unpredictable consequences for the Syrian population and neighboring countries, as well as U.S. allies and forces in the region. The United States and other countries have assessed that the Syrian government has used chemical weapons against opposition forces in the country. The largest-scale use to date was on August 21, 2013. A U.N. inspection team began working in Syria on August 19, 2013 and completed their mission on August 31. Laboratories are currently analyzing samples collected by the inspectors."
CRS Report for Congress, R42848