In a series of six network interviews planned as part of a furious lobbying campaign in Congress, Obama also tried to get support from a strongly opposing public opinion on its military plans against the Arab country and said military threat was needed.

"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, Obama 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, part of a furious lobbying campaign aimed at winning support from dubious lawmakers as well as a war-weary public.

Amid deep divisions in Congress over the way forward, Obama met with Democrat and Republican senators on Tuesday and gave a televised address to the nation that night.

US Senate Majority Leader Harry Reid announced he would not file for a test vote on a resolution to strike Syria, following a day of disappointing debates.

Reid said he is delaying a key vote on authorizing the use of force in Syria to let President Barack Obama publicly address the issue.

At least three lawmakers who had been among the many in the undecided column announced on Monday they would oppose the move to authorize the use of force.

"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. Missouri Republican Roy Blunt also announced his opposition.

In the House, one of two female Iraq war veterans in Congress announced opposition to military strikes.

SHI/SHI