House leaders line up behind Obama
Earlier Tuesday, the leaders of both parties in the House of Representatives emerged from a White House meeting earlier Tuesday to support Obama's call for American strikes.
House Speaker John Boehner, R-Ohio, told reporters the use of poison gas was "a barbarous act" to which only the United States is capable of responding. House Minority Leader Nancy Pelosi, D-California, added that Washington must respond to actions "outside the circle of civilized human behavior."
But in a written statement later, Boehner said it is up to Obama "to make his case to the American people and their elected representatives" -- including securing support from individual members.
"All votes authorizing the use of military force are conscience votes for members, and passage will require direct, continuous engagement from the White House," the speaker said.
No vote is scheduled before Congress returns from its summer recess on Monday. Kerry defended the delay to seek congressional authorization, saying the move gives the United States time to make its case while adding pressure on al-Assad.
"This is working," Kerry said. "There are defections taking place. There's great uncertainty in Syria. We are building support, a greater understanding, and I would far rather be playing our hand than his at this point in time."
Most of the focus of administration lobbying has been on the House. In the Senate, a Democratic source familiar with Majority Leader Harry Reid's thinking told CNN that Reid is confident any authorization measure will pass his chamber. The source said it is likely 60 votes will be needed to overcome a filibuster, and Reid thinks the votes are there.
U.N. chief calls for end to Security Council 'stalemate'
The United Nations has said more than 100,000 people -- including many civilians -- have been killed in Syria since a popular uprising spiraled into a civil war in 2011. Syrian opposition activists reported another 107 dead on Monday, mostly in Damascus and its suburbs.
New U.N. figures Tuesday point to the staggering impact the war has had on the nation.
The number of Syrians who have fled their war-ravaged country has risen above 2 million, the U.N. refugee agency reported, an increase of nearly 1.8 million people over the past 12 months.
But at the United Nations, Secretary-General Ban Ki-moon urged Security Council members to await test results on the samples collected by U.N. inspectors.
"We should avoid further militarization of the conflict and revitalize the search for a political settlement," Ban said. "I take note of the argument for action to prevent further uses of chemical weapons. At the same time, we must consider the impact of any punitive measure on efforts to prevent further bloodshed and facilitate a political resolution of the conflict. The turmoil in Syria and across the region serves nobody."
He urged member states to work through the Security Council, where Syrian allies Russia and China are expected to block any call for military action.
"The Security Council has a duty to move beyond the current stalemate and show leadership," Ban said. "This is a larger issue than the conflict in Syria. This is about our collective responsibility to humankind."
And al-Jaafari, the Syrian envoy, told CNN that all Syrians will be victims "of any escalation of the situation."
"We don't need wars. We need peaceful settlement of conflicts according to the charter of the United Nations," he said.
During Tuesday's hearing, Udall questioned whether the United States should be doing more to pressure Russia and China rather than going around the Security Council. Kerry said the Russians refused to sign off even on a resolution condemning a chemical attack that didn't assign blame.
"That doesn't mean we should turn our backs and say there's nothing we can do," Udall said.
But Kerry responded that if the Security Council is being blocked, "That doesn't mean we should turn our backs and say there's nothing we can do."
U.N. inspectors await test results
U.N. weapons inspectors left Syria on Saturday with samples that will help determine whether chemical weapons were used in the August 21 attack. Those samples will all be at laboratories by Wednesday and will be tested "strictly according to internationally recognized standards," Ban told reporters at U.N. headquarters.
Those tests could take up to three weeks -- and even then, those tests will only determine whether a gas attack took place, not who was behind it.
"If confirmed, the use of chemical weapons by anyone, under any circumstances, will be a serious violation of international law and an outrageous war crime," Ban said.