"Syria today is not about choosing between two sides but rather about choosing one among many sides," Joint Chiefs Chairman Gen. Martin Dempsey wrote this week to a member of Congress.
"It is my belief that the side we choose must be ready to promote their interests and ours when the balance shifts in their favor. Today, they are not," he said in the August 19 letter.
Dempsey also warned that even limited military action in Syria could lead to deeper involvement.
Late on Friday, a defense official said the United States had added a Navy destroyer to the eastern Mediterranean fleet.
The USS Ramage arrived to replace the USS Mahan, but the Mahan is going to stay around a bit longer, so temporarily there will be four. The USS Gravelly and USS Barry remain.
These ships are all equipped with the Tomahawk Land Attack Missiles, a long-range subsonic cruise missile used to attack land targets.