Russia making a 'big mistake'

US President Barack Obama said Friday that Russia's decision to send military advisors and equipment to Syria extended a strategy "doomed to failure," and could kill off already stagnant peace efforts.

Obama said that Russia's decision to ramp up its military presence in war-torn Syria represented a "doubling-down" of Moscow's support for Syrian President Bashar al-Assad.

US officials say Russia has sent ships, armored personnel carriers and naval infantry to the country in recent weeks, a move which Obama said showed Assad was worried his grip on power is slipping.

"The strategy that they are pursuing right now, doubling down on Assad, I think is a big mistake," Obama said at an event marking the 14th anniversary of the 9/11 attacks.

"We are going to be engaging Russia to let them know that you can't continue to double down on a strategy that is doomed to failure."

He said Russia -- which has a large and restive Muslim population in the North Caucasus -- faced more of a threat from the Islamic State group than the United States does.