Lawmakers briefed on the plans have indicated an attack is all but certain. And Obama advisers said the president was prepared to strike unilaterally, though France has said it is ready to commit forces to an operation in Syria because the use of chemical weapons cannot go unpunished.
The U.S. does not have United Nations support to strike Syria, and U.N. Secretary-General Ban Ki-moon has urged restraint. "Diplomacy should be given a chance and peace given a chance," he said Thursday.
Expected support from Britain, a key ally, evaporated as Parliament rejected a vote Thursday endorsing military action in Syria. And diplomats with the 22-nation Arab League said the organization does not support military action without U.N. consent, an action that Russia would almost certainly block. The diplomats spoke anonymously because of rules preventing them from being identified.
"Presidents always need to be prepared to go at it alone," said Rudy deLeon, who was a senior Defense Department official in the Clinton administration.
"The uninhibited use of the chemical weapons is out there, and that's a real problem," said deLeon, now senior vice president of security and international policy at the liberal-leaning Center for American Progress in Washington. "It can't be ignored, and it certainly creates a dilemma. I think (Obama) had to make the red-line comment, and so Syria has acted in a very irresponsible way."
The nearly nine-year war in Iraq that began in 2003, which Obama termed "dumb" because it was based on false intelligence, has encouraged global skittishness about Western military intervention in the Mideast. "There's no doubt that the intelligence on Iraq is still on everybody's mind," deLeon said.
Both Republican George H.W. Bush and Democrat Bill Clinton had U.N. approval for nearly all of their attacks on Iraq years earlier. Even in the 2003 invasion, which was ordered by Republican George W. Bush, 48 nations supported the military campaign as a so-called coalition of the willing. Four nations — the U.S., Britain, Australia and Poland — participated in the invasion.