Washington's top general has said the crash of a U.S. surveillance drone after being intercepted by Russian jets showed Moscow's increasingly aggressive behavior while Russia warned Washington that flying drones near Crimea risked escalation.

A day after the U.S. drone went down over the Black Sea, defense ministers and military chiefs from the U.S. and Russia held rare telephone conversations on Wednesday with relations at their lowest point in decades over Moscow's invasion of Ukraine.

Moscow's Defence Minister Sergei Shoigu told his U.S. counterpart, Lloyd Austin, that American drone flights by Crimea's coast "were provocative in nature" and could lead to "an escalation ... in the Black Sea zone," a ministry statement said.