PARIS (Reuters) – France criticized Russia on Thursday for calling into question an international inquiry into who is to blame for chemical weapons attacks in Syria.

Russia has questioned the work and future of the joint inquiry by the U.N. and the Organization for the Prohibition of Chemical Weapons (OPCW), and said it would decide whether to support extending the mandate after investigators submit their next report.

“We cannot accept that the credibility and independence of these mechanisms are challenged on the grounds that their conclusions are not suitable for Russia,” French foreign ministry spokeswoman Agnes Romatet-Espagne told reporters.

“This undermines the international consensus that it is our responsibility to build to stop the use of these weapons in Syria.”

The inquiry, known as the Joint Investigative Mechanism (JIM), is due to report by Oct. 26 on who was responsible for an April 4 attack on the opposition-held town of Khan Sheikhoun that killed dozens of people.

France, Britain and the United States have accused Syrian President Bashar al-Assad’s government of being behind the attack and the probe is expected to back those claims.

The United States said on Wednesday it would push the United Nations Security Council to renew within days the JIM’s mandate, setting the stage for a likely showdown with Russia, which backs Assad and denies Assad has used chemical weapons.

France, under President Emmanuel Macron, has been pushing for closer cooperation with Moscow, especially over Syria, and has said dialogue with Russia on enforcing a 2013 Security Council resolution to prevent the use of chemical weapons in Syria was one of its priorities.

“The JIM (already) concluded in its August and October 2016 reports the responsibility of the Syrian armed and security forces in three cases of chlorine use and Islamic State in one case. The methodology of the investigation is indisputable,” Romatet-Espagne said.