Inspectors from the global chemical weapons watchdog have been unable to access sites controlled by Russian Federation and the Syrian regime in the town of Douma to investigate an attack on 7 April that killed dozens and prompted US-led missile strikes on Friday night.
Russian Federation is denying any attempt to prevent access or scrub the site and is instead blaming the delay on the USA led airstrikes.
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.
"This is the latest conjecture of our British colleagues", said Sergei Ryabkov, Russia's deputy foreign minister. Relief organisations say dozens of men, women and children were killed.
The press conference also came after the he Organisation for the Prohibition of Chemical Weapons held emergency talks on the alleged atrocity, which prompted Western air strikes on Syria on Saturday, and Russian Federation and Syria stalled access to Douma citing security concerns.
Syrian and Russian officials had warned of "pending security issues to be worked out before any deployment could take place", Uzumcu said.
The weekend missile strikes by the US, Britain, and France were in response to an alleged chlorine and sarin gas attack in Douma on April 7 in which 40 people were said to have been killed.
Inspectors from The Hague-based OPCW travelled to Syria last week to inspect the site, but have yet to gain access to Douma, which is now under regime control.
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"It is our understanding the Russians may have visited the attack site", United States ambassador Ken Ward said.
"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", he said.
Kenneth Ward, the USA ambassador to the OPCW, raised these fears on Monday, drawing a denial from the Russian foreign minster, Sergei Lavrov, who told the BBC: "I can guarantee that Russia has not tampered with the site". "Unfettered access essential. Russia & Syria must cooperate", the delegation tweeted.
The limited scope of the strikes and the fact that Damascus had time to remove key assets thanks to prior warning given by the West to Syria regime ally Russian Federation, also drew sceptical comments from analysts.
Moscow blamed the delay on the air strikes, in which the United States, France and Britain targeted what the Pentagon said were three chemical weapons facilities.
Syria and Russian Federation say there are still security concerns to take care of before the team can inspect the area.
"We called for an objective investigation".