French Foreign Minister Jean-Marc Ayrault said 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, 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 OPCW found that Syrian government troops were responsible for two toxic gas attacks and Islamic State militants used sulfur mustard gas.
Ayrault had 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. "We have to send concrete signals and really make a commitment … There can be no shadow of a doubt."
The U.N. report 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.
Ayrault said France was pressing for a condemnation by the Security Council and to create the conditions for resuming political dialogue.
Russia said on Thursday it was prepared to work with the United States on a response to the UN report.
