Making the case Friday for the strikes, Secretary of State John Kerry noted that Turkey, France and Australia have condemned the suspected chemical attacks and said "we are not alone in our will to do something about it and to act."
"As previous storms in history have gathered, when unspeakable crimes were within our power to stop them, we have been warned against the temptations of looking the other way," Kerry said. "History is full of leaders who have warned against inaction, indifference and especially against silence when it mattered most."
He added: "It matters here if nothing is done. It matters if the world speaks out in condemnation and then nothing happens."
Some lawmakers in Obama's party hedged in supporting an attack with little foreign backup.
Senate Armed Services chairman Carl Levin, a Democrat, persisted in calling for weapons and other lethal aid to be given to vetted Syrian rebel groups to help fight Assad's forces. He said that should happen "while we seek international support" for limited strikes.
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