WASHINGTON -- The administration insisted Thursday that President Barack Obama has both the authority and the determination to make his own decision on a military strike against Syria, even as a growing chorus of lawmakers demanded an opportunity to vote on the issue and Britain, the United States' closest ally, appeared unlikely to participate.
Britain's sudden withdrawal came after Prime Minister David Cameron, deserted by rebels in his own Conservative Party, lost a parliamentary vote for provisional authorization for military action in Syria. Mr. Cameron, who had strongly backed Mr. Obama's pledge to ensure that Syria would face "consequences" for its alleged use of chemical weapons, said he would respect Parliament's will.
Many in his government attributed the vote loss to the legacy of British participation in the 2003 U.S.-led invasion and subsequent occupation of Iraq, based on false claims about weapons of mass destruction.
A statement distributed by the White House said: "The U.S. will continue to consult with the U.K. government -- one of our closest allies and friends. As we've said, President Obama's decision-making will be guided by what is in the best interests of the United States. He believes that there are core interests at stake for the United States, and that countries who violate international norms regarding chemical weapons need to be held accountable."
Both privately and publicly, administration officials continued to portray Mr. Obama as edging closer to a decision to launch a limited cruise-missile strike on Syrian military targets. As a fifth U.S. warship entered the Mediterranean, Mr. Obama's top national security officials briefed congressional leaders on evidence that they say proves that Syrian President Bashar Assad's government killed hundreds of civilians in an Aug. 21 chemical weapons attack outside Damascus.
But as more time has elapsed between the Syrian attack and the much-previewed U.S. retaliation, the window for questions and demands from Congress, international allies and the news media has opened wider. Nearly 200 House members from both parties have signed letters calling upon the president to seek formal congressional approval for military action.
Others agree with the chairman of the Senate Foreign Relations Committee, Robert Menendez, D-N.J., who said in an interview that the president has "certain powers even under the War Powers Act that he can use [in] the national interest of security, and he can act." But while many would support action against the Syria regime, Mr. Menendez said, "they want [Obama] to come before them and explain it."
Tennessee Sen. Bob Corker, the Foreign Relations panel's senior Republican, said after Thursday's administration briefings that he would "support surgical, proportional military strikes given the strong evidence" of chemical weapons use. But Mr. Corker said "whatever limited action is taken should not further commit the U.S. in Syria beyond the current strategy" of supporting moderate opposition forces fighting Mr. Assad's military.
He called for continued consultation, and said the administration would be "far better off if they seek authorization based upon our national interests, which would provide the kind of public debate and legitimacy that can only come from Congress."
In a phone call Thursday with House Speaker John Boehner, R-Ohio, Mr. Obama "briefed the speaker on the status of deliberations over Syria," while Mr. Boehner "sought answers to concerns, ... including the legal justification for any strike, the policy and precedent such a response would set, and the objectives and strategy for any potential action," said Boehner press secretary Brendan Buck. "Only the president can answer these questions, and it is clear that further dialogue and consultation with Congress, as well as communication with the American public, will be needed," Mr. Buck said.
Senate Majority Leader Harry Reid, D-Nev., has been in regular contact with Mr. Obama in recent days, Senate aides said.
The White House has said it will provide Congress with an additional classified assessment of Mr. Assad's responsibility for what it has called an "undeniable" chemical attack and will publicly release an unclassified version this week.
But support for a military strike appeared to be quickly waning. Even in France, where President Franois Hollande just days ago said Syria should be "punished," officials called for a delay in any action until United Nations weapons inspectors, who are in Syria, complete their investigation.
U.N. Secretary-General Ban Ki-moon told reporters in Vienna that the investigators will continue their on-site work near Damascus today and leave Syria on Saturday. Mr. Ban said he expects an immediate report from the inspectors, but he has made clear that their mission is to determine only whether a chemical attack occurred, not to assign blame.
At the U.N. Security Council, where Russia and China on Wednesday rejected a British-drafted resolution authorizing the use of force against Syria, the five permanent members met again Thursday. But the meeting, called at Russia's request, lasted less than an hour and didn't result in any action, according to U.N. officials.
State media reported that two Russian warships were traveling to the eastern Mediterranean. Russia, Mr. Assad's principal foreign backer along with Iran, has a naval base in the Syrian port of Tartus, although many personnel have reportedly been evacuated in recent days.
Iran's new president, Hassan Rouhani, said his government would cooperate with Russia to prevent a strike against Syria, which he called an "open violation" of international law.
Iraq has loomed large in the debate over the wisdom of an attack on Syria and the U.S. right to conduct one. In a now-infamous U.N. presentation in February 2003, then-Secretary of State Colin L. Powell offered audio intercepts, photographs and testimony from anonymous witnesses as proof that Saddam was developing chemical, biological and, perhaps, even nuclear weapons -- despite evidence to the contrary offered by U.N. investigators.
One month later, U.S. troops invaded, backed by a multinational force whose leading contributor was Britain. Within a year, evidence of Iraqi weapons of mass destruction had collapsed.
U.S. military officers have deep doubts about impact, wisdom of a U.S. strike on Syria. Page A-4