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 defence missile system to Syria but has frozen further shipments.

He suggested that Russia might sell the potent missile systems elsewhere if Western nations attack Syria without UN Security Council backing.

The interview Tuesday night at Putin's country residence outside the Russian capital was the only one he granted prior to the summit of G-20 nations in St. Petersburg, which opens Thursday.

The summit was supposed to concentrate on the global economy but now looks likely to be dominated by the international crisis over allegations that the Syrian government used chemical weapons in the country's civil war.

Putin said he felt sorry that U.S. President Barack Obama cancelled a one-on-one meeting in Moscow that was supposed to have happened before the summit. But he expressed hope the two would have serious discussions about Syria and other issues in St. Petersburg.