Russia warned Western powers on Monday against any military intervention in Syria, saying the use of force without a U.N. mandate would be a grave violation of international law.

Foreign Minister Sergei Lavrov said Moscow had no plans to be drawn into a military conflict over the civil war in Syria and that Washington and its allies would be repeating “past mistakes” if they intervened in Syria.

Russia is Syrian President Bashar al-Assad’s key ally and one of its main arms suppliers, and a veto-wielding member of the Security Council.

Expressing concern about statements suggesting NATO had the right to intervene after a chemical attack without securing the approval of the United Nations, Lavrov said the unapproved use of force would “sharply aggravate” the situation. He urged the West not to go down the “dangerous path” it had taken several times before.

He also added that Russia has no plans to be drawn into a military conflict over Syria.

French Foreign Minister Laurent Fabius noted that Russia and China would probably veto a U.N. Security Council vote to allow strikes against Syria. British Foreign Secretary William Hague, however, said it would still be possible to respond to a chemical weapon attack without the Security Council’s backing.