"The president wants the facts," spokesman Jay Carney said, "and I'm not going to set a timeline, because the facts need to be what drives this investigation, not a deadline."
Syrian officials denied Friday that their forces had used chemical weapons against rebels.
Hanging over the Obama administration's approach to the new intelligence reports are hard lessons learned from the Iraq war, when faulty intelligence drew the United States into a lengthy and expensive conflict. Obama, as a candidate for U.S. Senate, opposed the Iraq war and made ending the conflict a priority in his first term.
Lawmakers on Capitol Hill appeared to be drawing on similar lessons from more than a decade ago. Many who sounded the alarm about Iraq's Saddam Hussein and the possibility of weapons of mass destruction -- and strongly stood with President George W. Bush's decision to invade Iraq -- were far more muted Friday.
Following a closed-door briefing by Secretary of State John Kerry, they stressed the importance of building international support for any military move against Syria, rather than unilateral U.S. action. The sectarian strife in Iraq and the lawlessness in Libya after the killing of longtime leader Moammar Gadhafi in 2011 stand as sober reminders of what can happen.
"We want to do everything we can to avoid putting boots on the ground," said Rep. Dutch Ruppersberger of Maryland, the senior Democrat on the House Intelligence Committee. "I don't think that we, just as the United States, want to go in to another war."
Polling shows war-weary Americans are broadly opposed to the notion of the U.S. military intervening in Syria. Just one in five said the United States has a responsibility to do something about the fighting there, according to a CBS News poll conducted in late March.
However, faced with more specific scenarios, Americans appear more willing to back U.S. involvement. In an ABC News/Washington Post poll late last year, 63 percent said they would support military intervention if the Syrian government used chemical weapons against its people.
Roughly the same number said they would support using American military aircraft to create a no-fly zone if no ground troops were involved.
The White House faces a limited choice of military options to help the rebels oust Assad.
Arming the rebels would run into the reality that a military group fighting alongside them has pledged allegiance to al-Qaida. Establishing a no-fly zone poses a significant challenge, as Syria possesses an air-defense system far more robust than the United States and its allies overwhelmed in Libya two years ago.
Thus far, the Obama administration has limited its assistance to the Syrian rebels to nonlethal aid, including military-style equipment such as body armor and night-vision goggles. The United States also has deployed about 200 troops to Jordan to assist that country's military, and has participated in NATO's placement of Patriot missile batteries near the border in Turkey to protect against an attack from Syria.