The White House said it would like to see Russia engage with the international coalition fighting Islamic State militants in Syria, rather than build up its own military presence there.
White House spokesman Josh Earnest said September 15 that President Barack Obama had not spoken to Russian President Vladimir Putin about the issue, but would do so when the president "determines that it would advance our interests."
Putin said earlier in the day that it's impossible to defeat IS without cooperating with the Syrian government, and that Russia would continue to provide military assistance to Damascus.
But U.S. officials are concerned that Russia's increasing military presence in Syria is aimed more at strengthening the government of President Bashar al-Assad rather than seeking a transition to a new political leadership or fighting militant groups.
Bolstering Assad is "destabilizing and counterproductive," Earnest said. "What we would prefer to see from the Russians is a more constructive engagement with the 60-member coalition that's led by the United States that's focused on degrading and ultimately destroying ISIL."