Obama made his comments as a glimmer of a possible diplomatic solution appeared after months of defiance from the Russian-backed government of President Bashar Assad in Syria.
In a rapid response, Senate Majority Leader Harry Reid cited "international discussions" in unexpectedly postponing a test vote originally set for today on Obama's call for legislation backing a military strike.
In a series of six network interviews planned as part of a furious lobbying campaign in Congress, Obama said statements suggesting that Syria might agree to surrender control of its chemical weapons stockpile were a potentially positive development.
At the same time, he said they were yet another reason for lawmakers to give him the backing he is seeking.
"If we don't maintain and move forward with a credible threat of military pressure, I do not think we will actually get the kind of agreement I would like to see," he said on CNN.
In a separate interview with NBC, the president took the step of conceding he may lose his campaign in Congress for legislation authorizing a military strike.
"I wouldn't say I'm confident" of the outcome, he said.
"I think it's fair to say that I haven't decided" on a next step if Congress turns its back, the president told NBC.
Obama picked up a smattering of support but also suffered a reversal when Sen. Johnny Isakson, R-Ga., announced he had switched from a backer of military action to an opponent.
"They're in tough shape. It is getting late," said Rep. Peter King, R-N.Y., after he and other lawmakers emerged from a closed-door meeting with administration officials. The New York Republican favors the legislation that Obama wants, but he said the president didn't need to seek it and now must show that a strike "is in America's national security interest."
Classified briefings for lawmakers just back from vacation, the public release of cringe-inducing videos of men, women and children writing in agony from the evident effects of chemical gas, and a half-dozen network news interviews featuring Obama were folded into the White House bid to avert a humiliating defeat over the next 10 days.
Obama met with members of the Congressional Black Caucus during the day, and arranged a trip to the Capitol as well as a prime-time speech from the East Room of the White House today.
Others came down on the other side of the question.
"I will vote 'no' because of too much uncertainly about what comes next," said Sen. Lamar Alexander, a Tennessee Republican. "After Step A, what will be steps B, C, D and E?" he added, reflecting concerns that even the limited action Obama was contemplating could lead to a wider war.
In the House, one of two female Iraq war veterans in Congress announced opposition to military strikes.
"As a soldier, I understand that before taking any military action, our nation must have a clear tactical objective, a realistic strategy, the necessary resources to execute that strategy, including the support of the American people, and an exit plan," said Rep. Tulsi Gabbard, D-Hawaii. She said Obama's plan "fails to meet any of these criteria."
The public opinion polling was daunting for Obama.
An Associated Press poll showed that 61 percent of those surveyed want Congress to vote against authorization of U.S. military strikes in Syria and 26 percent want lawmakers to support such an action, with the remainder undecided.
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