Secretary of State John Kerry made a forceful case on Tuesday for a military strike in Syria, saying the evidence is clear the Assad regime used chemical weapons and America cannot "be spectators to a slaughter."
"This is not the time for armchair isolationism," Kerry said, in testimony before the Senate Foreign Relations Committee. The hearing marked the first by Congress to consider Obama's request for authorization for use of force in Syria.
Though tens of thousands have been killed in the course of the Syrian civil war, Obama administration officials and top-ranking lawmakers are arguing that it is now in the "national security interest" for the U.S. to get more involved, and punish the Assad regime for using chemical weapons.
Senate Foreign Relations Committee Chairman Bob Menendez, D-N.J., said that failing to do so would embolden America's enemies. He said failing to act would send Iran and others the message that the U.S. is "not serious" about its own goals of stopping the proliferation of chemical weapons.
"At the end of the day, our national security is at stake," he said.
The hearing comes after the Obama administration won support for a strike on Syria from top congressional leaders, including House Speaker John Boehner.
Boehner, emerging from a White House meeting, said the chemical weapons attack last month "has to be responded to."
"The use of chemical weapons is a barbarous act. It's pretty clear to me that the United Nations is unable to take action, NATO not likely to take action. The United States for our entire history has stood up for democracy and freedom for people around the world," Boehner said. "I'm going to support the president's call for action."
Minutes later, House Democratic Leader Nancy Pelosi told reporters that she, too, feels Syrian President Bashar Assad has "crossed a line."
House Republican Leader Eric Cantor said definitively that he plans to vote in favor of giving Obama authorization to use military force.
Senate Democratic Leader Harry Reid has also indicated his support.
The only hold-out appears to be Senate Republican Leader Mitch McConnell.
He said in a written statement that "while we are learning more about his plans, Congress and our constituents would all benefit from knowing more about what it is he thinks needs to be done-and can be accomplished-in Syria and the region."
The statements backed Obama's argument that a limited missile strike on the Assad regime would be in the U.S. national security interest, by deterring the use of chemical weapons. Obama, as the White House meeting began, said he was confident he would win congressional support.
Others, though, have cast the president's decision to seek congressional backing as a big risk. Some have described his chances of winning approval as "50-50." While congressional leaders and senior members of key committees are getting onboard, the president faces skepticism from both liberal Democrats and some Tea Party-aligned Republicans. Others worry the administration is not going far enough with a limited strike that the administration admits is not aimed at regime change.
Sen. John Cornyn, R-Texas, on Tuesday urged Obama to deliver a national address explaining to the American people why the U.S. should launch an attack.
"The president needs to explain in detail what vital national interests are at stake, his plan for securing these interests and a clear definition of what success looks like in Syria," he said in a written statement.
On Tuesday night, the resolution on Syria had been updated to expressly bar the use of U.S. troops in "combat operations" and limit the authorization to 30 days.