Russia and Syria have stalled access to Douma by international experts seeking to probe an alleged poison gas attack there, citing security concerns, a British diplomat said Monday.
The claim came as the global chemical arms watchdog held emergency talks on the alleged atrocity, which prompted Western air strikes on Syria on Saturday.
The head of the Organisation for the Prohibition of Chemical Weapons (OPCW), Ahmet Uzumcu, told the closed-door meeting his inspectors had failed to gain access to the site so far, the British ambassador to the Netherlands told reporters.
Uzumcu said "the Syrian regime and the Russians were citing security concerns," ambassador Peter Wilson told a press conference.
The Russians and Syrians "have not been able to guarantee the security of the delegation to go to Douma at this point," Wilson added, saying no timeline had been given for when they could visit.
The talks at the OPCW's headquarters come two days after a wave of punitive missile strikes in Syria launched by Western powers after the alleged April 7 toxic arms attack on Douma.
The team had been expected to begin their field work on Sunday, but they met with officials at their Damascus hotel instead and a strict media blackout was imposed on their schedule.
The Kremlin dismissed claims that Russia was impeding access.
"We consider such accusations against Russia to be groundless," President Vladimir Putin's spokesman Dmitry Peskov said, adding that Moscow was in favour of "an impartial investigation".
The missiles that US, French and British warships fired on suspected chemical facilities Saturday constituted the biggest Western attack against the regime in the seven-year war.
The targeted sites were largely empty, and were all said to be facilities for chemical weapons storage or production.
In the Syrian capital, thousands of people gathered on the main Umayyad square to express their support for President Bashar al-Assad in the aftermath of the missile strikes.
But at the OPCW, France urged nations to boost the organisation's work so it can dismantle Syria's "secret" toxic weapons programme.
Following recent alleged attacks, "we all know, Syria has maintained a secret chemical programme since 2013," French ambassador Philippe Lalliot said.
"The facts are there, and they defy the most obscene lies and the most absurd denials," he said.
He added that priority must be given to helping the OPCW "complete the dismantling of the Syrian program."
The limited scope of the weekend strikes and the fact that Damascus had time to remove key assets thanks to prior warning given by the West to the Syrian regime's ally Russia, have drawn scepticism however.
The trio of Western powers that carried out the strikes warned they would repeat the operation if Damascus used chemical weapons again, while Putin warned any fresh strikes would "provoke chaos".
With no further strikes planned for the time being, the West already appears to be shifting its focus to renewed diplomatic action, with a new resolution to be debated at the UN Security Council on Monday.
"The bottom line for me is that this latest strike changed nothing," said Nabeel Khoury, a former US diplomat and currently a fellow at the Atlantic Council think tank.
"In my opinion, it was a staged drama, orchestrated by Trump and Putin, for each to save face," he said.
The attack on Douma, in which most experts say chlorine as well as an agent such as sarin were used, killed at least 40 people, according to local medics.
Holdout fighters from the Islamist group Jaish al-Islam subsequently surrendered their heavy weapons and left, saying that the chemical attack forced them to accept a Russian-brokered transfer deal.