President Vladimir Putin warned the West against taking one-sided action in Syria but also said Russia "doesn't exclude" supporting a UN resolution on punitive military strikes if it is proved that Damascus used poison gas on its own people.

In a wide-ranging interview with the Associated Press and Russia's state Channel 1 television, Putin said Moscow has provided some components of the S-300 air defense missile system to Syria but has frozen further shipments.

He suggested that Russia may sell the potent missile systems elsewhere if Western nations attack Syria without UN Security Council backing. The interview comes ahead of the summit of G-20 nations in St. Petersburg, which opens tomorrow.