Matthew Rowland, the British ambassador to the organization, said it “deplores the fact that Syria will assume the presidency of the Conference on Disarmament, given the regime’s consistent and flagrant disregard of international nonproliferation and disarmament norms and agreements.”

The conference was created in 1979, and one of the most significant treaties it negotiated was the 1993 Chemical Weapons Convention, which bans the production, stockpiling or use of chemical weapons.

Syria formally submitted to the convention in September 2013, less than a month after a sarin attack in Ghouta killed 1,400 people. Under a deal brokered by the United States and Russia, it surrendered stocks of chemical agents used in the production of sarin gas and other weapons, but subsequent attacks by the Syrian military hardened suspicions that it had not handed over its entire arsenal.

United Nations investigators said they had documented more than 30 chemical weapons attacks by the Syrian government since the start of the civil war, including an attack with sarin-like agents in April 2017 that killed at least 83 people.