Ken Ward, the usa ambassador to the OPCW, claimed Monday the Russians had already visited the site and "may have tampered with it", a charge Moscow rejected. British Prime Minister Theresa May accused the two countries - whose forces now control the town east of Damascus - of trying to cover up evidence.
Top Jaish al-Islam official Mohammad Alloush accused the regime on Wednesday of "erasing proof of the chemical (attack) in Douma".
State Department spokeswoman Heather Nauert said Tuesday that US officials could not confirm whether the OPCW team had entered Douma and that any delay degrades evidence.
The OPCW visit to Douma came hours after Syrian media reported airstrikes Tuesday on government military installations in the central Homs region and the suburbs of Damascus, but the military later said a false alarm had set off air defense systems.
Journalists were allowed access to Douma on Monday. Gen. Yuri Yevtushenko of the Russian military's Reconciliation Center in Syria.
Speaking at an emergency session of the OPCW at its headquarters in The Hague, Ahmet Uzumcu said the team had deployed to Douma to carry out a security assessment of the area ahead of the inspectors' visit.
Although US intelligence sources have now admitted they do not have "absolute certainty" that the attack at Douma used sarin gas.
Chemical arms experts blocked from site of Syria attack
Therefore allegations of this towards Russian Federation are groundless", Kremlin spokesman Dmitry Peskov said. French Foreign Minister Jean-Yves Le Drian said he welcomed the EU's unanimous backing.
The inspection was initially delayed by Russian Federation and Syria, who reportedly refused to allow the chemical weapons team to enter the city.
"As far as I understand, what is hampering a speedy resolution of this problem is the consequences of the illegal, unlawful military action that Great Britain and other countries conducted on Saturday", he said.
Confusion has swirled over when a fact-finding team of experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) will be able to enter the city of Douma, prompting concerns that repeated delays could stymie its mission.
The Russian ambassador to the United Nations, Vassily Nebenzia, said that the idea of establishing a mechanism to determine responsibility for the use of chemical weapons is "futile" since Washington and its allies already identified who the "culprits" are behind the gas attacks, referencing the US-led attack on Syria.
A government media tour on Monday of Douma, the biggest town in the former rebel enclave of eastern Ghouta just outside Damascus, revealed severe destruction and the plight of residents who had survived years of siege.
Damascus and Moscow insist the April 7 incident was fabricated.
"People started throwing water over each other".
According to some people said to be eyewitnesses, unknown people then entered the bombed building where victims were being treated and shouted "gas, gas". A odd smell lingered, nine days after the attack.