'The team has not yet deployed to Douma, ' he said at the OPCW's headquarters in The Hague.
Russian Federation is denying any attempt to prevent access or scrub the site and is instead blaming the delay on the US led airstrikes.
The OPCW team has so far held meetings with Syrian officials but is not believed to have started field work in Douma, where holdout rebels surrendered their weapons and agreed to leave after the alleged attack.
The mission of experts from the Organization for the Prohibition of Chemical Weapons (OPCW) to probe the use of chemical weapons in Syria's Douma stalled on Monday amid USA accusations against Russian Federation that it meddled with the site of the attack.
The United States, Britain and France carried out a wave of strikes against the Syrian regime on Saturday a week after the suspected deadly gas attack on the rebel-held Damascus suburb of Douma, in which 40 people were said to have been killed.
Its team on the ground also faced the risk of arriving too late to a site where much of the evidence may have always been removed or tampered with.
The United States, United Kingdom and France launched missile strikes on a number of targets in Syria at 4 a.m. local time on Saturday in retaliation for the so-purported the chemical use.
The army said that troops discovered weapons factories, arms depots, tunnels and food storage places.
"I can guarantee that Russian Federation has not tampered with the site", he told the BBC.
Syrian state media made no mention of the strike on Dumair.
Despite polls showing scant support for the move, May said it had been her "responsibility as prime minister to make these decisions", while Macron also defended his move as part of his constitutional powers.
According to Kirilov, one of the filmed children, who has been reportedly targeted by alleged chemical weapons, is a child of one of the officials working in the medical facility and has not even left the building.
And the United States called for a clear condemnation by the OPCW of "the Syrian government for its reign of chemical terror".
A fact-finding mission by the UN's chemical weapons watchdog has arrived in Damascus.
Douma and the sprawling eastern Ghouta region near the capital, Damascus, had been under rebel control since 2012 and was a thorn in the side of President Bashar Assad's government for years. Photographs and video from Douma documented victims suffering from symptoms consistent with exposure to toxic chemicals, such as asphyxiation and foaming at the mouth, the officials said.
Britain's Ambassador Peter Wilson said in The Hague that the United Nations had cleared the inspectors to go but they had been unable to reach Douma because Syria and Russian Federation had been unable to guarantee their safety.
Russian ambassador Shulgin repeated the accusations telling reporters in The Hague that Douma residents had not been able to produce "a single body".