Russian President Vladimir Putin has warned America and its allies against taking one-sided action in Syria.
He said any military strikes without UN approval would be "an aggression".
US President Barack Obama has called for punitive action in response to an alleged chemical weapons attack.
Mr Putin said Russia did not rule out supporting a UN Security Council resolution authorising force, if it was proved "beyond doubt" that the Syrian government used chemical weapons.
On Tuesday evening, members of the Senate Foreign Relations Committee agreed on a draft resolution backing the use of US military force.