Russian Foreign Ministry spokeswoman Maria Zakharova said Wednesday that there are "Russian military experts in Syria who are instructing (the Syrians) on the use of the military systems being delivered" to the Syrian government.
Russian Foreign Minister Sergei Lavrov on Friday urged members of the so-called international coalition against Daesh in Iraq and Syria to cooperate with the Syrian armed forces.
However, Obama said on Friday that "the strategy they're pursuing right now of doubling down on Assad is a mistake,” a claim Russia rejects.
"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 during a town hall with US military personnel.
Obama said that the Russian help would not impact on the US "core mission" to fight Daesh terrorists in Syria, but added that "it could prevent us from arriving to a political settlement."
Meanwhile, Lavrov said it is impossible to "defeat Islamic State (Daesh) with air strikes only," adding that "it's necessary to cooperate with ground troops and the Syrian army is the most efficient and powerful ground force to fight the IS."
Lavrov has denied allegations that Russia is engaged in a military buildup in Syria as suggested by the United States and the NATO.
US Secretary of State John Kerry, in a phone call on Wednesday, warned his Russian counterpart against Moscow’s move in Syria, saying it “could lead to greater violence and even more instability in Syria," according to the US State Department spokesman John Kirby.
Moscow and Washington have had major differences over the crisis in Syria. While the Kremlin lends support to Damascus in its fight against Daesh, the White House wants to see President Bashar al-Assad toppled; Press TV reported.