A Russian official says a team of chemical weapons experts is set to make a visit Wednesday to the site east of Syria's capital where a suspected chemical attack killed dozens of people earlier this month.
The investigators from the Organization for the Prohibition of Chemical Weapons arrived in Syria on Saturday, but so far have not been able to begin their work in Douma.
The U.S. envoy to the OPCW, Ken Ward, said Monday it was his understanding Russia had already visited the site and he raised concerns of tampering before the OPCW carries out its fact-finding mission.
Russian Foreign Minister Sergei Lavrov denied the accusation, telling the BBC he guarantees Russia "has not tampered with the site."
Lavrov said that evidence cited by the United States, Britain and France to justify last Saturday's missile attack on three Syrian chemical weapons facilities was based "on media reports and social media." He denied any chemical weapons attack had occurred, accusing Britain of staging the attack.
Russia further blamed the Saturday airstrikes for the delays in the OPCW team being able to access Douma.
Syrian media reported another missile attack early Thursday in Homs province, saying government air defenses shot down most of the missiles fired at an air base. The reports did not say who was responsible, and the U.S. military said neither it nor the coalition it leads was operating in that area at the time.
OPCW Director-General Ahmet Üzümcü said Monday that Russian and Syrian officials had informed the team that there are "still pending security issues to be worked out before any deployment could take place" to Douma.
In Moscow, Russia's Deputy Foreign Minister Sergei Ryabkov said the mission was not allowed in because it lacked approval from the United Nation’s Department for Safety and Security.
U.N. officials in New York disputed the claim.
"The United Nations has provided the necessary clearances for the OPCW team to go about its work in Douma," said U.N. spokesman Stephane Dujarric. "We have not denied the team any request for it to go to Douma."
He added that U.N. Secretary-General António Guterres is very supportive of the investigation.
"The secretary-general wants to see the fact-finding mission have access to all the sites it needs to have access to, so that we can have the most thorough and full picture of the facts," Dujarric said.
EU foreign policy chief Federica Mogherini said ahead of a ministerial meeting there is a clear need to push for re-launching a U.N.-led peace process for Syria. At the U.N. Security Council, France has proposed a new draft resolution that addresses three key aspects of the conflict — chemical weapons, humanitarian issues and the political process.
"So, this is our road map, and we will work very hard, in good faith, in good spirit, to listen to everybody, in order to try to move ahead with our draft resolution and move forward toward an inclusive political settlement of the crisis," France’s envoy François Delattre told reporters Monday.
Margaret Besheer contributed to this report.