Britain and its allies were squaring off against Russia on Tuesday in a high-stakes diplomatic drive to give the world's global chemical watchdog the power to identify those behind toxic arms attacks.
The meeting opened in The Hague as inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) are also expected to unveil soon a long-awaited 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.
British Foreign Secretary Boris Johnson was to head up his country's delegation to a rare special session of the OPCW's top policy-making body, and was due to address the session later in the day.
"We want to strengthen the Organisation entrusted with overseeing the ban on chemical weapons," the British delegation said in a tweet.
"We want to empower the @OPCW to identify those responsible for chemical weapons attacks."
London called the talks of the OPCW's state party members in the wake of the nerve agent attack on former Russian double agent Sergei Skripal and his daughter in the English town of Salisbury, which Britain and its allies have blamed on Russia.
There has however been growing international concern about repeated allegations of the use of poison gases in the Iraq and Syria conflicts, compounded by the 2017 assassination of the North Korean leader's half-brother in a rare nerve agent attack in Kuala Lumpur airport blamed on Pyongyang.
It is feared that although deadly chemical weapons were once largely shunned as taboo after decimating forces during World War I, their use is once again becoming gradually normalised in the absence of any effective way of holding perpetrators to account.
Opening the session, the conference chairman, Abdelouahab Bellouki, said, those responsible for chemical weapons attacks "need to be punished on the basis of true and strong evidence".
"In spite of different and divergent positions and opinions, we are all committed to constructive cooperation ... in order to rid once and for all the world of chemical weapons."
Tensions already ran high early Tuesday, and the talks will move behind closed doors on Wednesday and possibly linger on until Thursday for a key vote on the British draft decision. It is only the fourth time in the body's history that such a special session has been convened.
Russia has already denounced the meeting, and the head of the delegation, Georgy Kalamanov, said Moscow would not support Britain's draft decision and will unveil its own, state news agency RIA Novosti reported.
"We believe that the powers that Britain wants to give to the OPCW are the powers of the UN Security Council and this is the only body which has a right to make such decisions," he said.
But others, including France and the United States, believe it is time the organisation's role evolved.
"The mandate of the OPCW must be adapted to the challenges of the 21st century," said a French diplomat ahead of the talks, asking not to be named.
"It was conceived in an entirely different context to independently verify the proper destruction by the major powers during the Cold War of their chemical weapons stocks."
A two-thirds majority, minus any abstentions, is needed for Britain's draft to pass, with about 153 countries out of the OPCW's 193 members registered to attend.
But sources say Russia is already working behind the scenes to defeat Britain's proposal.
Moscow wielded its veto power late last year at the UN Security Council to effectively kill off a previous joint UN-OPCW panel aimed at identifying those behind attacks in Syria.
Before its mandate expired in December, the panel known as the JIM (Joint Investigative Mechanism) had determined that the Syrian government had used chlorine or sarin gas at least four times against its own civilians. The Islamic State group used mustard gas in 2015.
Outgoing OPCW head Ahmet Uzumcu has said the current situation of impunity is "unsustainable", warning "a culture of impunity cannot be allowed to develop around the use of chemical weapons".