WASHINGTON -- President Barack Obama abruptly changed course Saturday and postponed a military strike against the Syrian government in retaliation for a chemical weapons attack so he could seek authorization first from a deeply skeptical Congress.
In one of the riskiest gambles of his presidency, Mr. Obama effectively dared lawmakers to either stand by him or, as he put it, allow President Bashar Assad of Syria to get away with murdering children with unconventional weapons. By asking them to take a stand, Mr. Obama tried to break out of the isolation of the past week as he confronted taking action without the support of the United Nations, Congress, the public or Britain, a usually reliable partner in such international operations.
"I'm prepared to give that order," Mr. Obama said in a hurriedly organized appearance in the Rose Garden as U.S. destroyers armed with Tomahawk missiles waited in the Mediterranean Sea. "But having made my decision as commander in chief based on what I am convinced is our national security interests, I'm also mindful that I'm the president of the world's oldest constitutional democracy."
Although congressional leaders hailed his decision to seek the permission of lawmakers who had been clamoring for a say, the turnabout leaves Mr. Obama at the political mercy of House Republicans, many of whom have opposed him at every turn and have already suggested that Syria's civil war does not pose a threat to the United States. His decision raises the possibility that he would be the first president in modern times to lose a vote on the use of force, much as Prime Minister David Cameron of Britain did in Parliament last week.
Mr. Obama overruled the advice of many of his aides who worried about just such a defeat. Republican congressional officials said House Speaker John Boehner told the president Saturday that if a vote were taken immediately, the Republican-controlled chamber would not support action. Interviews with more than a dozen members of Congress made clear that the situation was volatile even in the Senate, where Democrats have a majority.
"Obama hasn't got a chance to win this vote if he can't win the majority of his own party, and I doubt he can," Rep. Tom Cole, R-Okla., said in an interview. "Democrats have been conspicuously silent. Just about his only support is coming from Republicans. He is a war president without a war party."
Yet the debate may also put on display the divisions in the Republican Party between traditional national security hawks and a newer generation of lawmakers, particularly in the House, resistant to entanglements overseas and distrustful of Mr. Obama.
"It will be an uphill battle for the president to convince me because I think he has handled this entire situation quite poorly," said Rep. Tim Griffin, R-Ark. "And frankly I am reluctant to give him a license for war when, with all due respect, I have little confidence he knows what he is doing."
Even Sens. John McCain of Arizona and Lindsey Graham of South Carolina, two Republicans who have pressed Mr. Obama to intervene more aggressively in Syria, said Saturday that they might vote no because the president's plan is too limited.
"We cannot in good conscience support isolated military strikes in Syria that are not part of an overall strategy that can change the momentum on the battlefield," they said in a statement.
Against that backdrop, the wording of the authorization of force may be critical. White House officials drafted a proposed measure that tried to strike a balance between being too expansive and too restrictive, and sent it to Congress on Saturday evening.
The proposal would empower Mr. Obama to order military action to "prevent or deter the use or proliferation" of chemical or biological weapons "within, to or from Syria" and to "protect the United States and its allies and partners against the threat posed by such weapons." Still, White House officials indicated Mr. Obama might still authorize force even if Congress rejects it.
As Syrian forces braced for attack, the president's decision effectively put it off for more than a week, because Congress is not due back in Washington until Sept. 9. Mr. Obama did not push Congress to come back sooner, and House leaders opted to keep to their schedule. Senate leaders were considering coming back Friday for a weekend of debate.
In the interim, though, lawmakers will be in their home states, where polls show their constituents are not eager to attack Syria.
"One constituent said to me, 'It is horrendous that these children were killed, but they are being killed in other ways also. What's the difference?' " said Sen. Susan Collins, R-Maine.
Presidents in modern times have used military force both with and without congressional authorization. Although Mr. Obama said as a candidate that a president has no power to launch a military attack except to stop "an actual or imminent threat to the nation," he acted unilaterally in Libya in 2011 and had no plans to act differently in Syria this time. But he found it much harder to proceed alone, given the British vote and in the face of polls showing the vast majority of Americans want Congress to decide.
Even allies like Sen. Tim Kaine of Virginia, one of Mr. Obama's earliest supporters for president and his hand-picked Democratic Party chairman, publicly argued that he had to come to Congress for permission.
"The worst thing we can do is put people out on that limb and ask them to potentially risk their lives based on equivocal political support," Mr. Kaine said.
In making his request, Mr. Obama argued more forcefully than he ever had for military action against Syria, echoing some of the moral outrage expressed by Secretary of State John Kerry a day earlier.
"What message will we send if a dictator can gas hundreds of children to death in plain sight and pay no price?" he asked.
Mr. Obama also dispatched Mr. Kerry, Defense Secretary Chuck Hagel and others to brief senators by telephone Saturday and authorized a classified briefing on Capitol Hill today. Mr. Kerry was also booked onto the Sunday TV news programs to make the case.
The surprise Syria vote will come as a deeply divided Congress was already gearing up for bitter fights this fall over federal spending, the debt ceiling, immigration and government surveillance. And it will invite a complicated, multilayered debate crossing party lines and involving other actors like Israel supporters who worry that failure to follow through in Syria will embolden Iran.