The stage is being set for the biggest foreign policy vote in Congress since the Iraq War as White House officials met with lawmakers this weekend to discuss the possibility of U.S. military action in Syria.
President Barack Obama will hold a special briefing with lawmakers on Capitol Hill Monday, some say the president has a hard sell.
Obama's weekend announcement surprised many political observers. The decision marked a stark turnabout for the White House, which had appeared on the verge of ordering a strike against Syria.
"While I believe I have the authority to carry out this military action without specific congressional authorization, I know that the country will be stronger if we take this course and our actions will be even more effective," Obama said.
Secretary of State John Kerry defended the president's decision to unleash U.S firepower, citing new evidence against President Bashar al-Assad's regime.
"From first responders in east Damascus...we have signatures of sarin in their hair and blood samples," Kerry said. "We cannot allow Assad to be able to gas people with impunity."
Lawmakers are being briefed by the White House Monday, but convincing a war-weary Congress and the American public will be difficult.
"In my mind, it's far from settled. It's not something that should be undertaken lightly," Rep. Mike Burgess, R-Texas, said. "Certainly the mood in the district that I represent is 'do not do this.' And I honestly didn't hear anything that told me I ought to have a different position."
"People want to know there is not going to be a military entanglement like in Iraq or Afghanistan. We've got a very skeptical public," Rep. Illeana Ros-Lehtinen, R-Fla.
But the president appears determined, saying doing nothing is not acceptable.
"What message will we send if a dictator can gas hundreds of children to death in plain sight and pay no price?" Obama asked.
Congress will vote on the issue when it returns on Sept. 9.
Meanwhile, critics argue the president's decision is really about the 2014 congressional election and trying to make House Republicans look bad if they vote against the strike.