But Sen. Ron Wyden, D-Ore., remained undecided. "What the effects of a military strike would be are not clear," he said.
The Senate Foreign Relations Committee voted 10-7 Wednesday to authorize the "limited and specified use" of the U.S. armed forces against Syria, backing a resolution that restricts military action to 90 days and bars American ground troops from combat.
Obama's deputy national security adviser, Tony Blinken, picked up the sales pitch for the absent president Thursday, appearing on several morning news shows.
In an appearance on MSNBC, Blinken said he believes the American people will be more supportive of Obama's request once they see the Syrian situation as a separate and distinct problem as opposed to viewing it "in the prism of the last decade" of wars in Iraq and Afghanistan.
"This is not open-ended. This is not boots on the ground. This is not Afghanistan. This is not Iraq. This is not even Libya," Blinken said.
He said that if the United States does not stand up to Assad and against the use of chemical weapons, some world figures will believe "it's OK to use them with impunity."
Secretary of State John Kerry, testifying for the second consecutive day before Congress, insisted that the U.S. military response would be restricted as Americans fatigued by more than a decade of war in Iraq and Afghanistan show little inclination to get involved in Syria.
"I don't believe we're going to war, I just don't believe that," Kerry told the House Foreign Affairs Committee, citing the ground troops and long-term commitment that he said wars entail. "That's not what we're doing here. The president is asking for permission to take a limited military action, yes, but one that does not put Americans in the middle of the battle."
In the Senate, five Republicans, including potential presidential candidates Rand Paul and Marco Rubio, and two Democrats opposed the resolution, which is expected to reach the Senate floor next week. The timing of a vote is uncertain.
Obama personally lobbied Sen. Chris Murphy, D-Conn., calling the lawmaker last Sunday. Murphy was a vote against in committee.
Paul, a Kentucky conservative with strong tea party ties, has threatened a filibuster, although he acknowledged that proponents have the votes to prevail in the Senate, and he pinned his hopes on the House.
The notion of a contained operation has failed to sway many Republicans and Democrats in the House, who question why the U.S. should get involved now in a Syrian civil war that has killed an estimated 100,000, displaced millions and is in its third year. While House Speaker John Boehner, R-Ohio, and Majority Leader Eric Cantor, R-Va., have expressed support for military action, but rank-and-file Republicans remain reluctant or outright opposed.
Kerry told the Foreign Affairs Committee that he believed Obama would address the nation on Syria in the next few days. The president returns home from overseas Friday night.
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.
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