Britain and the United States have led an effort to empower the world's chemical-weapons watchdog to identify who is behind toxin attacks, triggering strong opposition from Russia and Syria.
Moscow and Damascus have denied charges that they used chemical weapons in recent months, and argued there should be no change to the mandate of the Organization for the Prohibition of Chemical Weapons (OPCW).
"We all hoped that these terrible instruments of death would never be used again," British Foreign Secretary Boris Johnson told the organization's top policy-making body in The Hague.
"But the tragic reality is that chemical weapons have been used and are being used all over again."
In the absence of any mechanism to identify who is behind any such attacks, Britain has proposed that the watchdog be empowered to do so.
The OPCW is expected to soon unveil its report into an alleged sarin-and-chlorine-gas attack in April in the Syrian town of Douma. Medics and rescuers say 40 people were killed, blaming the attack on the government of President Bashar al-Assad.
Johnson also highlighted what he called the "appalling" nerve-agent attack in March on former Russian double agent Sergei Skripal and his daughter, Yulia, which London blamed on Moscow.
"None of us wants our children to grow up in a world where the use of chemical weapons becomes normalized," Johnson said.
But Moscow said the British proposal went against international law and that the chemical attack in Douma was "faked," while continuing to deny any involvement in the Skripal attack.
"The only international body or international court who can decide who would be guilty when we are dealing with members of the United Nations is the Security Council," Russian minister Georgy Kalamanov said.
Delegates are expected to vote on Britain's proposal behind closed doors on June 27.