President Obama on Monday expressed doubts about whether he would be able to rally enough support on Capitol Hill for a resolution authorizing U.S. force against Syria.

“I wouldn't say I'm confident,” Obama told NBC News, in one of six interviews he conducted to rally support for his call to punish Syria for using chemical weapons.

The pessimistic public comments about the political backing for his Syria push marked a shift from the White House’s line in recent days that lawmakers would rally behind the president.

Obama said in his interviews that final votes could be delayed to rally enough support for his plan.

The president also said that a Russian proposal to have Syria hand over control of its chemical stockpile to international observers could “absolutely” avert a strike if Damascus followed through.

Senate Majority Leader Harry Reid, D-Nev. announced on Monday shortly after Obama’s interviews aired that he would delay a planned procedural vote on Syria to give the president more time to make his case.

Reid insisted that he had enough votes for cloture, but said it was important to allow the president time to sway undecided lawmakers.

Obama also told NBC that he has not yet decided whether he will proceed with an attack against Syria if lawmakers reject his plan.

Obama acknowledged that it was a risky move taking his Syria proposal to Congress but one which was necessary given the importance of his decision.

"I've made my decision about what I think is best for America's national interests," he said, "but this is one where I think it's important for me to pay close attention to what Congress and the American people say."

Obama will address the nation from the White House Tuesday, hoping to stem a tide of criticism against his plan to strike strongman Assad's regime in retaliation for the dictator reportedly using chemical weapons against his own people.

Rather than embolden his cause, the more administration officials make their case on Syria, the more congressional opposition seems to have hardened in recent days, as polls show a majority of Americans oppose intervention.

But Obama and his surrogates continue to press their appeals to skittish lawmakers, with UN Ambassador Susan Rice speaking at a think tank and former Secretary of State Hillary Clinton publicly backing the president’s plan on Monday.

Obama is also scheduled to have lunch with Republicans and Democrats on Capitol Hill Tuesday, just hours before addressing the nation.