Russian officials on October 13 questioned the United Nations inquiry into who is to blame for a toxic gas attack in Syria and threatened it might not support extending the investigating team's mandate if it is not satisfied with the resulting report.
The probe was carried out by the UN and the Organization for the Prohibition of Chemical Weapons (OPCW), known as the Joint Investigative Mechanism (JIM).
The JIM was authorized by the Security Council in 2015 and had its mandate renewed for another year in 2016. The mandate will expire in the middle of November unless further renewed.
The dispute centers on who is to blame for an April 4 attack on the opposition-held town of Khan Sheikhoun that killed dozens.
The United States, France, and Britain have accused Syrian President Bashar al-Assad's forces of carrying out the air assault on Khan Sheikhoun, a conclusion supported by an OPCW fact-finding mission.
The United States subsequently launched a missile attack on Syria’s Shayrat airfield after concluding that government aircraft had departed from the airfield loaded with sarin gas for the attack on Khan Sheikhun.
However, Russia and Syria have blamed the attack on Syrian antigovernment rebels.
Mikhail Ulyanov, the Russia Foreign Ministry's head of nonproliferation, told a briefing at the UN that the sarin attack was most likely caused by a bomb set off on the ground in the village itself and not by an air strike.
Ulyanov complained that investigators failed to search for traces of the banned nerve gas on their visit to the airfield this week, which he said was a “scandalous” situation and an indication of the JIM team’s unwillingness to carry out a “qualitative investigation.”
"A reliable investigation is simply impossible without sampling," Ulyanov said.
A spokesman for the UN investigative team declined to comment.
Ulyanov said Moscow will await the team's report on October 26 and then decide whether to block renewal of the investigative team's authority when it comes up next month.
The JIM has already determined that Syrian government forces were responsible for three chlorine gas attacks in 2014 and 2015 and that Islamic State (IS) militants used mustard gas in attacks.
The Syrian government has repeatedly denied using chemical weapons during the country’s more than 6-year-old civil war.
Assad’s government agreed to destroy its chemical weapons in 2013 as part of an agreement brokered by Russia and the United States.