The Senate panel's vote marked the first formal response in Congress, four days after Obama unexpectedly put off an anticipated cruise missile strike against Syria and instead asked lawmakers to unite behind such a plan.
The vote capped a hectic few days in which lawmakers first narrowed the scope of Obama's request and then widened it.
Sen. John McCain, R-Ariz., a proponent of aggressive U.S. military action in Syria, joined forces with Democratic Sen. Chris Coons of Delaware to add a provision calling for "decisive changes to the present military balance of power on the ground in Syria."
At their urging, the measure was also changed to state that the policy of the United States was "to change the momentum on the battlefield in Syria so as to create favorable conditions for a negotiated settlement that ends the conflict and leads to a democratic government in Syria." McCain, who long has accused Obama of timidity in Syria, argued that Assad will be willing to participate in diplomatic negotiations only if he believes he is going to lose the civil war he has been fighting for more than two years.
Associated Press writers Julie Pace and Josh Lederman in Russia and Bradley Klapper, Alan Fram, Deb Riechmann, Kimberly Dozier, Lolita C. Baldor and Andrew Taylor in Washington contributed to this report.