Decision day loomed Wednesday at the world's chemical weapons monitor as Western powers frantically sought behind closed doors to rally support for moves to beef up the watchdog's powers.
Britain, backed by allies such as the United States and France, is leading a high-stakes drive to enable the independent Organisation for the Prohibition of Chemical Weapons (OPCW) to attribute blame for any use of toxic substances in Syria.
But they have met fierce opposition from Russia, backed by Syria and Iran. Both Moscow, the main ally of Syrian President Bashar al-Assad, and Damascus stand accused by the international community of using chemical weapons in recent months -- allegations they deny.
The move comes amid growing frustration at the lack of a mechanism to punish perpetrators amid repeated recent confirmed attacks with chlorine, sarin and even mustard gas in Syria and Iraq, and the use of rare nerve agents in Britain and Malaysia.
"Today is decision day ... for the @OPCW in The Hague. We will vote at 14:40," the British delegation to the OPCW said in a tweet, as the talks moved behind closed doors after a 12-hour public session on Tuesday.
In a war of words on Twitter, mirroring the tensions inside the cavernous World Forum where the meeting is being held, the Russian embassy hit back that "deception is perhaps the word of the day".
Britain had failed to provide any evidence that Moscow was behind the nerve agent attack on Russian ex-spy Sergei Skripal and his daughter in Salisbury in March, it said.
Instead Britain has "embroiled their allies in the blatant campaign against Russia. Now they try to drag the #OPCW in their games."
Both sides were believed to be furiously working behind the scenes to win support, with one diplomatic source telling AFP "it's very intense inside".
By the end of the morning session, four amendments to the British proposal tabled by Iran, Venezuela, Kazakhstan and Belarus had been decisively defeated, the British delegation tweeted.
"Belarus' amendment to the Decision we and others tabled to strengthen @OPCW would have gutted it and made it impossible to identify the perpetrators of CW attacks," British ambassador Peter Wilson said in a tweet.
"It was voted down. Only 23 countries voted for it 78 voted no," he added, with the other amendments also being defeated by similar margins.
Dutch Foreign Minister Stef Blok warned the repeated use of chemical weapons was a "black cloud" hanging over the OPCW which has destroyed 96 percent of the world's toxic arms stockpiles.
"The result was terrible human suffering, but also the risk of a 'new normal': a situation where perpetrators consider themselves untouchable," he said, in a copy of his speech provided to AFP.
Despite optimism among Western diplomats, there are no guarantees the vote will go in favour of Britain and its allies.
Brazil summed up the unease felt by several countries at giving the watchdog greater powers outside the forum of the UN Security Council.
"Any change, if it is to be adopted, should ... by no means make up for protracted impasses or dysfunctionalities in other international bodies," said Ambassador Regina Maria Cordeiro Dunlop on Tuesday.
Late last year, Russia wielded its veto power at the UN Security Council to effectively kill off a joint UN-OPCW panel aimed at identifying those behind suspected chemical attacks in Syria.
The OPCW is also due to publish a report soon into an alleged gas and sarin attack in the Syrian town of Douma. Moscow and Damascus insist the attack was fake, staged by the Syrian rescue volunteers known as the White Helmets.
A two-thirds majority, minus any abstentions, is needed for Britain's proposal to pass at the OPCW meeting on Wednesday.
"We all hoped that these terrible instruments of death would never be used again," British Foreign Secretary Boris Johnson told the meeting on Tuesday.
"But the tragic reality is that chemical weapons have been used and are being used all over again."
The Hague, Netherlands | AFP