The upper house of the Russian parliament has given President Vladimir Putin approval to use the Russian air force in Syria, according to state media.
"The Federation Council unanimously supported the President's request - 162 votes in favor of granting permission," Kremlin Chief of Staff Sergey Ivanov said, according to ITAR-Tass.
The vote came after a request by Syrian President Bashar al-Assad for military assistance in fighting ISIS, Ivanov said.
"They could start at any moment," an official said.
"They are ready."
Pentagon spokesman Peter Cook told reporters Tuesday that Secretary of Defense Ash Carter directed his staff to "open lines of communication with Russia on de-confliction."
The timing of these discussions is to be worked out in the coming days.
The purpose of the discussions is "to ensure the safety of coalition air crews," he said.