Senior State Department official Wendy Sherman and military officials were seen entering a congressional conference room, carrying a chart and other material they were to present to lawmakers who've already returned to Washington. Dozens of members attended.
The Senate Foreign Relations Committee plans a meeting Tuesday, according to its chairman, Sen. Bob Menendez, D-N.J. The Senate Armed Service Committee will gather a day later, said Oklahoma Sen. Jim Inhofe, the top Republican on the panel.
Kerry confidently predicted that lawmakers would back limited military strikes.
"The stakes are just really too high here," he said.
Kerry was asked repeatedly in the broadcast interviews what Obama would do if Congress didn't give its consent. He said he believed lawmakers would recognize the grave implications for letting a chemical weapons attack go unchecked and what that might mean for U.S. efforts to force North Korea to get rid of its nuclear weapons and prevent Iran from acquiring such capability.
"We are not going to lose this vote," Kerry said. "The credibility of the United States is on the line."
Obama is likely to find stronger support in the Democrat-controlled Senate than the GOP-dominated House, yet faces complicated battles in each. Some anti-war Democrats and many tea party-backed Republicans are opposed to any intervention at all, while hawks in both parties, such as McCain, feel the president must do far more to help Syria's rebels oust Assad from power.
"It can't just be, in my view, pinprick cruise missiles," McCain told CBS' "Face the Nation."
In an interview with an Israeli television network, McCain said Obama has "encouraged our enemies" by effectively punting his decision to Congress. He and fellow Republican Sen. Lindsey Graham of South Carolina have threatened to vote against Obama's authorization if it is too limited.
On the other end of the spectrum, an unusual coalition of foreign policy isolationists, fiscal conservatives and anti-interventionists in both parties opposes even limited intervention for fear that might draw the United States into another costly and even bloody confrontation.
The White House request to Congress on late Saturday speak only of force to "deter, disrupt, prevent and degrade" the Assad regime's ability to use chemical weapons.
"I think it's a mistake to get involved in the Syrian civil war," said Sen. Rand Paul, R-Ky.
Echoing that sentiment, Sen. Chris Murphy, D-Conn., questioned: "Does a U.S. attack make the situation better for the Syrian people or worse?"
Paul expected the Senate to "rubber-stamp" Obama's plan, while he said it was "at least 50/50 whether the House will vote down involvement in the Syrian war." Inhofe predicted defeat for the president.
Despite the intense gridlock in Congress over debt reduction, health care, immigration and other issues, some lawmakers were more optimistic about the chances of consensus when it came to a question of national security.
Rep. Peter King, R-N.Y., who criticized Obama for not proceeding immediately against Assad, said he'd vote "yes" and believed the president should be able to build a House majority over the next several days.
"At the end of the day, Congress will rise to the occasion," added Rep. Mike Rogers, R-Mich. "This isn't about Barack Obama versus the Congress. This isn't about Republicans versus Democrats. This has a very important worldwide reach."
Sen. Tim Kaine, D-Va., said Congress and the American people would support action once Obama finishes making his case. Sen. Saxby Chambliss, R-Ga., said if Obama doesn't do that, he won't get his authorization.
"He's got to come out and really be in-depth with respect to the intelligence that we know is out there," said Chambliss, the top Republican on the Senate Intelligence Committee. "He's got to be in-depth with respect to what type of military action is going to be taken and what is our current strategy?
In his TV interviews, Kerry reiterated Obama's oft-repeated promise not to send any American troops into Syrian territory.
Polls show significant opposition among Americans to involvement, and several lawmakers have cited the faulty intelligence about weapons of mass destruction that led up to President George W. Bush's 2003 Iraq invasion as justification of the need for lengthy debate before U.S. military action.
Kerry, who voted to authorize Bush's 2003 Iraq invasion but then opposed it in his unsuccessful presidential bid a year later, rejected any comparisons to America's recent wars.
"This is not Iraq. This is not Afghanistan. There is nothing similar in what the president is contemplating," Kerry said. "There are others who are willing to fight, others who are engaged. And the issue here is not whether we will go and do it with them, it's whether we will support them adequately in their efforts to do it."
Kerry appeared on CBS, NBC's "Meet the Press," CNN's "State of the Union," ''Fox News Sunday" and ABC's "This Week." Paul was on NBC, Rogers and Murphy were on CNN, King and Inhofe were on Fox, and Chambliss and Kaine were on CBS.
Associated Press writer Laurie Kellman in Washington contributed to this report.
U.S. assessment on Syria: http://apne.ws/14etnyn
- Wyoming ranked third in US in percentage of...
- Test anxiety: How cold feet are ruining your...
- Hometown pastor says community stands by...
- Sen. Harry Reid's retirement recalls his...
- 'A marvellous work and a wonder': A look back...
- Drownings along Rio Grande spike after...
- O'Malley: Presidency 'not some crown'...
- Hundreds rally against Indiana law, say it's...
- Student loan recipients on 'strike'... 75
- Rep. Trey Gowdy: Hillary Clinton wiped... 49
- Sen. Harry Reid's retirement recalls... 40
- Indiana lawmakers try to quiet... 35
- Senate's Harry Reid announces he won't... 34
- Hundreds rally against Indiana law, say... 25
- Delete, erase, shred: The enemies of... 15
- O'Malley: Presidency 'not some crown'... 13