The comments came at the Organisation for the Prohibition of Chemical Weapons meeting held at the Hague as the watchdog has started its investigation on the site of the attack in Syria's Douma.
Russia may have tampered with the site of an alleged chemical weapons attack in Syria's Douma, the US envoy to the global watchdog said on Monday, urging the body to condemn the continuing use of banned chemical weapons.
The comments came during a closed-door meeting at the Organisation for the Prohibition of Chemical Weapons, convened after an April 7 attack in the town of Douma, outside the Syrian capital, in which dozens of people were allegedly killed with poison gas.
"It is long overdue that this council condemns the Syrian government for its reign of chemical terror and demands international accountability for those responsible for these heinous acts," US Ambassador Kenneth Ward said.
"It is our understanding the Russians may have visited the attack site. It is our concern that they may have tampered with it with the intent of thwarting the efforts of the OPCW Fact-Finding Mission to conduct an effective investigation."
OPCW starts its investigation, denied access
The United States, Britain and France fired more than 100 missiles at three alleged chemical weapons facilities on Friday, angering the Syrian regime's military backer Moscow, which threatened to retaliate.
President Donald Trump said the strikes had accomplished their aim of undermining efforts by the Syrian regime to produce and use chemical weapons again in violation of the Chemical Weapons Convention.
OPCW inspectors were expected to enter Douma aiming to collect samples, interview witnesses and document evidence to determine whether banned toxic munitions were used.
But the British delegation to the OPCW, citing the agency's director general, said Russia and the Syrian regime had not yet allowed inspectors access to the sites in Douma.
Russia's deputy foreign minister said the delay was due to US air strikes.
UK considers unfettered access essential. Russia and Syria must cooperate. https://t.co/OB5hp6qboS— UK Delegation OPCW (@UK_OPCW) April 16, 2018
It has been more than a week since the attack in which witnesses and Western governments described helicopters dropping sarin and chlorine bombs that killed many children and women hiding from clashes between rebels and regime forces.
A diplomatic source said evidence may have been removed while inspectors negotiated access with the Syrian regime.
The Syrian regime and Russia deny chemical weapons were used in the final offensive that captured Douma, a rebel-held territory east of Damascus.
Britain in the OPCW meeting
The British envoy to the OPCW said it had recorded 390 allegations of the use of banned chemicals in Syria since 2014, and that a failure by the OPCW to act risked allowing "further barbaric use of chemical weapons."
Syria joined the OPCW, the organisation tasked with monitoring adherence to the 1997 convention, in 2013 after a sarin gas attack that killed hundreds of people in Ghouta. The move was part of a joint Russian-US deal that averted military action threatened by then-president Barack Obama.
Russian Deputy Foreign Minister said any new US strikes in Syria would provoke a tougher response and will resist any new attempts.
Moscow had earlier vowed not to interfere in the work of a fact-finding mission sent to Syria.
"Russia confirms its commitment to ensure safe (sic) and security of the mission and will not interfere in its work," the Russian embassy in The Hague said in a tweet.
It also slammed the United States, saying the weekend strikes by the US, France and Britain on three facilities in Syria were a bid "to undermine the credibility" of the mission.
Russian President Vladimir Putin warned on Sunday that further Western attacks on Syria would bring chaos to world affairs, as Washington prepared to increase pressure on Russia with new economic sanctions.
Members of the 41-seat executive council of the OPCW were due to discuss the alleged use of prohibited toxins in Syria, but were not expected to reach any agreement about a response.
The organisation, which needs a two-thirds majority to take decisions, has been undermined by deep political division over the use of chemical weapons by the Syrian regime.
The OPCW inspectors will not assign blame for attacks. A joint United Nations-OPCW mission concluded that forces under Syrian regime leader Bashar al Assad had used chemical weapons several times in recent years, including in a sarin attack a year ago in the town of Khan Sheikhoun that killed nearly 100 people.