WASHINGTON (AP) — A Senate panel’s deep divide over giving President Barack Obama the authority to use U.S. military force against Syria underscores the commander in chief’s challenge in persuading skeptical lawmakers and wary allies to back greater intervention in an intractable civil war.

The administration was pressing ahead Thursday with its full-scale sales job, holding another round of closed-door meetings for members of Congress about its intelligence on Syria. On another continent, Obama was certain to face questions from world leaders when he arrives in St. Petersburg, Russia, for an economic summit.

The event’s host, Russian President Vladimir Putin, stands as a reminder of resistance to U.S. pleas for Moscow to intervene with its ally Syria and President Bashar Assad.

Obama has called for military action after the administration blamed Assad for a chemical weapons attack on Aug. 21 that it says killed more than 1,400 civilians, including at least 400 children. Other casualty estimates are lower, and the Syrian government denies responsibility, contending rebels fighting to topple the government were to blame.

Responding to Obama’s request, 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.

"I believe U.S. military action of the type contemplated here might prove to be counterproductive," Rubio said. "After a few days of missile strikes, it will allow Assad, for example, to emerge and claim that he took on the United States and survived."

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.

Republican Rep. Chris Collins said voters in his western New York district are "overwhelmingly against involvement." The freshman congressman is undecided.

"Really, I’m looking for the president to justify limited military strike and establish what are the objectives he’s seeking and what is the mission," Collins said in a phone interview.

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.

Speaking in Sweden on Wednesday, Obama left open the possibility he would order retaliation for the deadly chemical weapons attack even if Congress withheld its approval.

"I always preserve the right and responsibility to act on behalf of America’s national security," he told a news conference. In a challenge to lawmakers back home, he said Congress’ credibility was on the line, not his own, despite saying a year ago that the use of chemical weapons would cross a "red line."

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.

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Associated Press writers Julie Pace and Josh Lederman in Sweden and Bradley Klapper, Alan Fram, Deb Riechmann, Kimberly Dozier, Lolita C. Baldor and Andrew Taylor in Washington contributed to this report.