The world's foremost chemical weapons watchdog has granted itself new powers to assign blame for attacks, despite protests by Russia.
Until now, the Organisation for the Prohibition of Chemical Weapons (OPCW) could only say whether chemical weapons were used - but not who had used them.
Britain successfully argued that new powers were needed to deal with repeated chemical attacks in Syria.
Russia said the move went "beyond the mandate" of the watchdog.
It also said the organisation was facing an "artificially created crisis".
The members of the OPCW, however, voted in large numbers for the measure, winning the vote by 82 to 24 - exceeding the two-thirds majority needed.
Britain proposed the measure, and Foreign Secretary Boris Johnson said it would "strengthen the ban on chemical weapons and prevent impunity for their use".
An important step forward
Jonathan Marcus, BBC defence and diplomatic correspondent
This is an important step forward for arms control. It strengthens the unravelling consensus against the use of chemical weapons. It marks a victory for the rules-based international order, which itself is under increasing strain given the rise of populists and nationalism in many countries. But inevitably it will prove to be a new source of tension between Russia and the West.
Until now, chemical weapons inspectors working under the auspices of the OPCW were in a curious position. They could send teams to an alleged chemical weapons attack. They could take samples and draw their conclusions. They could determine whether indeed a chemical weapons incident had occurred. But whatever evidence they turned up, they could not point the finger at a particular country or non-state actor as the perpetrator.
That was, of course, a nonsense. It is like having a detective investigate a killing, only to conclude that yes indeed, murder most foul has been committed, but then being unable to identify the likely culprit.
Repeated allegations of chemical weapon use by Syria's government against rebels and civilians brought the issue into the international spotlight in recent months.
In April, the United States, UK, and France jointly bombed three Syrian government sites in response to the alleged chemical attacks.
The Syrian government, which is backed militarily by Russia, has repeatedly denied ever using chemical weapons.
International relations also frayed after the poisoning of former Russian double agent Sergei Skripal and his daughter on British soil.
UK investigators concluded that a Russian-developed military-grade nerve agent called Novichok was used in the attack in the city of Salisbury.
British authorities accused Russia of direct involvement; Russia is also the Syrian government's main ally.
Russian Industry Minister Georgy Kalamonov told Reuters news agency the OPCW was like a sinking ship.
"A lot of the countries that voted against the measure are starting to think about how the organisation will exist and function in the future," he said.