French Foreign Minister Jean-Marc Ayrault
French Foreign Minister Jean-Marc AyraultReuters

French Foreign Minister Jean-Marc Ayrault said Sunday he was pressing members of the UN Security Council, including Russia, to condemn the Syrian government after a report found Syrian troops had used chemical weapons.

"I see no reason that could be given, or any arguments that could be made, for not condemning the use of chemical weapons," he said, according to Reuters, when asked if Russia would support the resolution.

The Security Council is due to discuss the report next week.

A joint investigation by the United Nations and the global chemical weapons watchdog Organization for the Prohibition of Chemical Weapons (OPCW), released late last week, found that Syrian government troops were responsible for two toxic gas attacks and that Islamic State (ISIS) jihadists used sulfur mustard gas.

Ayrault told France's Le Monde newspaper in an interview published on Saturday that the report was a chance to push Russia to accept a resolution condemning the Syrian government and resume political negotiations.

He reiterated his concerns on Sunday after a meeting with the German and Polish foreign ministers, who all expressed concern about devastating humanitarian conditions in Aleppo.

Ayrault said that he had a recent long conversation with Russian Foreign Minister Sergei Lavrov, who had agreed that political negotiations were the only way to end the crisis in Syria.

"We cannot simply ignore this report," Ayrault said, according to Reuters. "We have to send concrete signals and really make a commitment ... There can be no shadow of a doubt."

Syria agreed to destroy its chemical weapons in 2013 under a deal brokered by Moscow and Washington, but the OPCW has since found chlorine has been "systematically and repeatedly" used as a weapon.

The UN investigation has set the stage for a Security Council showdown between the five veto-wielding powers, likely pitting Russia and China against the United States, Britain and France over whether sanctions should be imposed as a result.

Russia, a close ally of Syrian President Bashar Al-Assad, has repeatedly used its veto power at the Security Council to block resolutions against Assad.

But Moscow said on Thursday that it was prepared to work with the United States on a response to the UN report.