The president and top officials in the Cabinet and the White House repeatedly emphasize that the attack Obama is contemplating would be limited in scope and duration, with no ground troops involved, to avoid having the situation escalate into another prolonged war like in Iraq.
A Senate resolution passed by the Foreign Relations Committee limits any U.S. military response to up to 90 days and specifies no "boots on the ground."
"It's not the role of the United States military to go in and inflict regime change through military force because frankly when we do that we're responsible for everything that comes after," Deputy National Security Adviser Ben Rhodes told CNN, adding that "what we're going to do is protect our national security interests and that involves making it clear that nobody in the world should be able to use chemical weapons on the scale that we've seen in Syria and not face consequences."
At the same time, he acknowledged the risk of retaliatory attacks by Syria and allies including Iran and Hezbollah in Lebanon that could cause an undesired escalation.
"We're prepared for any contingency, of course, and the United States military is far stronger than any of Assad or his allies," Rhodes said, describing an outcome most feared by opponents of a U.S. attack.
In his interview with CNN later Monday, Obama downplayed the risk of retaliation by Syria, saying it lacked "a credible means to threaten the United States."
However, Obama said it was possible for Iran and Hezbollah to launch "asymmetrical strikes," but dismissed them as nothing more than "the kinds of threats that we are dealing with around the world."
Worry about an escalating conflict
Opponents question that premise, with veteran GOP Sen. Lamar Alexander of Tennessee announcing Monday he will oppose the resolution authorizing military force "because of too much uncertainty about what comes next."
"I see too much risk that the strike will do more harm than good by setting off a chain of consequences that could involve American fighting men and women in another long-term Middle East conflict," Alexander said in a statement.
Obama's decision to seek congressional authorization also bought him time to work on getting more support for a unified international response.
With news Monday that Russia was proposing that Syria turn over its chemical weapons stockpiles to international control, Obama said the idea could be either a potential breakthrough or an unacceptable stall tactic.
He asserted that his threat of a military attack prompted the new Russian offer.
"We have not seen these kinds of gestures up until now," Obama said, noting that he discussed the Syria issue last week with Russian President Vladimir Putin at the G20 gathering. "The fact that the U.S. administration and I have said we are serious about this, I think has prompted some interesting conversations."
The development also prompted a comment from former Secretary of State Hillary Clinton, considered the Democratic frontrunner in the 2016 presidential race if she decides to run, in her first public remarks on the Syrian issue since last month's attack.
Clinton said the "inhuman use" of chemical weapons demanded a strong international response "led by the United States," and like Obama, she credited the threat of U.S. military action for what would be "an important step" of Syria's possible surrendering of its chemical stockpiles.
In Congress, moderate Democratic Sen. Joe Manchin of West Virginia is proposing an alternative proposal to the attack authorization sought by Obama that would give Syria 45 days to sign on to the global convention banning chemical weapons use.
An aide to Manchin said Monday the senator has been promised a vote on the proposal, which is considered a way to avoid an embarrassing defeat for Obama if he can't mount enough support to pass the resolution authorizing military strikes.
Meanwhile, Senate Majority Leader Harry Reid was delaying the process of considering the resolution, a Democratic leadership aide said Monday. Reid originally had planned to hold an initial procedural vote on Wednesday, but the aide said the new Russian proposal caused the delay.
However, the opposition expressed in polls and CNN's ongoing survey of congressional support showed that the resolution faced an uphill battle to win approval.