Taken together, the new military moves appeared to be a demonstration that Russia has the ability to strike from virtually all directions in a region where it has been reasserting its power — from Iran, from warships in the Caspian Sea, from its base in the Syrian coastal province of Latakia and now from the Mediterranean.

The United States also asserted its military might in a new way, scrambling its aircraft to protect its forces, and those it is supporting, from Syrian government airstrikes. The Pentagon issued a blunt warning to the Syrian government after its warplanes struck a Kurdish-controlled region where American military personnel were on the ground.

"The Syrian regime would be well advised not to interfere with coalition forces or our partners," said Capt. Jeff Davis, a Pentagon spokesman.