Later Friday, Obama spoke by phone with French President Francois Hollande and British Prime Minister David Cameron. White House statements said in both calls, the leaders agreed the Syrian violation of chemical weapons bans cannot be tolerated, but only the statement on the call with Hollande said they agreed the Syrian regime must be held accountable.
While the British vote was a blow to Obama's hopes of getting strong support from key NATO allies and some Arab League states, regional NATO ally Turkey on Friday backed the U.S. contention that al-Assad's regime was responsible for the chemical attack.
"The information at hand indicates that the opposition does not have these types of sophisticated weapons," said Foreign Minister Ahmet Davutoglu. "From our perspective, there is no doubt that the regime is responsible."
Australia also weighed in, with Prime Minister Kevin Rudd saying the evidence against al-Assad was overwhelming and, "therefore, the focus now legitimately lies on the most appropriate from of international response."
Rudd said there has been "no request from the United States or any other country for a direct or indirect Australian military participation" in a possible strike against Syria.
Alone or together?
The White House has made clear that the United States will respond in some form to the use of chemical weapons. Previously, it ruled out U.S. troops on the ground or imposing a no-fly zone.
Sources have indicated a campaign of limited strikes by cruise missiles fired from U.S. naval ships in the region, targeting military command centers but not chemical weapons stockpiles, is the likely option.
The British Parliament vote and demands by other key European allies, including France and Germany, to put off a decision until after the U.N. inspectors report on what happened in Syria have slowed the response time.
Hollande told Le Monde newspaper that intervention should be limited and not be directed toward al-Assad's overthrow, a position also expressed by Obama.
Also Friday, former President Jimmy Carter, said "a punitive military response without a U.N. Security Council mandate or broad support from NATO and the Arab League would be illegal under international law and unlikely to alter the course of the war."
Defense Secretary Chuck Hagel has repeatedly said the United States will respond to Syria in concert with allies.
"Our approach is to continue to find an international coalition that will act together," he told journalists Friday in Manila, Philippines.
Skeptics of military action have pointed at the decision to use force in Iraq, when the United States government under Bush marched to war based on a thin claim that dictator Saddam Hussein was harboring weapons of mass destruction.
Opponents are conjuring up a possible repeat of that scenario in Syria, though the intelligence being gathered on the use of WMDs in Syria may be more sound.
An NBC News poll conducted Wednesday and Thursday indicated that 50% of the public says the United States should not take military action against Damascus in response to the Syrian government's alleged use of chemical weapons against its own citizens, with 42% saying military action would be appropriate.
But the survey suggested that if military action would be confined to air strikes using cruise missiles, support rises.
More than 160 legislators, including 63 of Obama's fellow Democrats, signed letters calling for either a vote or at least a "full debate" before any U.S. action.