Russia called on Friday for military-to-military cooperation with the United States to avert "unintended incidents" as it stages naval exercises off the coast of Syria, where U.S. officials believe Moscow is building up forces to protect President Bashar Assad.
The United States is using Syrian airspace to lead a campaign of airstrikes against the Islamic State group, and a greater Russian presence raises the prospect of the Cold War foes encountering each other on the battlefield.
Both Moscow and Washington say their enemy is the Islamic State group, whose Islamist fighters control large parts of Syria and Iraq. But Russia supports the government of Assad in Syria, while the United States says his presence makes the situation worse.