U.S. State Department official Frederic Hof told Congress on Wednesday that Mr. Assad's repression may allow him to hang on to power, but only for a short time.
Syrian rebels kill 27 troops; Canadians told to leave →
"The question now ... is whether or not we can shape [on outcome] on the margins," he added.
Ex-State Dept. official: U.S. will get 'sucked in' to Syria war →