The Organisation for the Prohibition of Chemical Weapons says there is a "serious threat" against world efforts to eradicate chemical armaments.
Syria and Russia are facing renewed pressure to come clean over alleged chemical weapons use as the global toxic arms body met in The Hague.
Damascus is still failing to declare its chemical weapons and admit inspectors, Organisation for the Prohibition of Chemical Weapons (OPCW) chief Fernando Arias said on Monday.
Syria denies the use of chemical weapons and insists it has handed over its weapons stockpiles under a 2013 agreement with the US and Russia, prompted by a suspected sarin gas attack that killed 1,400 people in the Damascus suburb of Ghouta.
But Syria was stripped of its OPCW voting rights in April after a probe blamed it for further poison gas attacks, and they will remain suspended until it has fully declared its chemical weapons and weapons-making facilities.
The nerve agent poisoning of jailed Kremlin critic Alexei Navalny in Russia meanwhile continues to pose a "serious threat" to world efforts to eradicate chemical armaments, Arias added.
Moscow had asked OPCW inspectors to come to Russia to investigate, but Arias said the visit had not taken place due to conditions set by the Russian authorities that were stricter than those imposed by other countries.
London and Washington meanwhile pushed Moscow and Damascus to comply with international laws.
"We call again on Russia and the Assad regime to comply with their obligations," Bonnie Jenkins, the US under secretary of state for Arms Control and International Security, said in a statement to the meeting.
British junior defence minister, Annabel Goldie, said Russia must not only answer questions on Navalny but also the Novichok poisoning of former KGB agent Sergei Skripal in Salisbury in 2018.
"There is no plausible explanation for these poisonings other than Russian involvement and responsibility," Goldie said.
Moscow has always denied involvement in both incidents.
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