WASHINGTON—President Barack Obama said on Saturday he has decided he should order a limited military strike against Syria, but in a move laden with political and diplomatic implications, he agreed in an about-face to solicit authorization for the mission from Congress.  Mr. Obama's announcement in a Rose Garden statement brought an unusually sudden halt to a military mobilization that for days had appeared on the cusp of a bombardment of Syria as punishment for its alleged use of chemical weapons on Aug. 21 that killed more than 1,400 people—including more than 400 children.  It also marked a jarring shift as president for Mr. Obama, whose senior aides have been saying that he would not seek congressional authorization and that he had the legal right to order the start of military strikes.  President Obama says that while he has decided that it is necessary for the U.S. to undertake a military strike on Syria, he will seek the support of Congress before doing so.  Mr. Obama said legislative leaders have agreed to hold a debate and a vote on the issue as soon as Congress returns, which currently is scheduled to be Sept. 9. Leaders in the Senate, where Democrats hold the majority, considered calling the chamber back to session before then.  The move places the president's Syria policy on an unknown course, subjecting it to a certain showdown on Capitol Hill where lawmakers are deeply divided on the issue and even more so over Mr. Obama himself.  By agreeing to a congressional debate, Mr. Obama faces some amount of risk that he will be handed a defeat by legislators, like that suffered by British Prime Minister David Cameron over Syria this past week.  By assuming that risk, Mr. Obama also faces the possibility of some consternation from U.S. allies, who have been pressed by the administration for support for its aims in Syria.  In Israel, President Obama's decision to postpone military action until after congressional approval was received with skepticism. Analysts on Israeli television blasted the president for making the U.S. appear weak in the region. An Israeli official warned that U.S. hesitation could embolden Iran's nuclear ambitions.  "There is concern that this will be seen in the region as the U.S. president hesitating to enforce his red lines and that that will send the wrong messages to other regional powers," said an Israeli official.  Senior Israeli officials have publicly backed U.S. intervention and Israel provided intelligence to Washington to support its case.  Mr. Obama will encounter world reaction when he leaves this week on a trip to Sweden and then to a meeting in Russia of the Group of 20 leading nations, where Syria is expected to be a major topic and where he could briefly meet Russian President Vladimir Putin, a staunch ally of Syrian President Bashar al-Assad and opponent of U.S. military action.  In Damascus's first official response to Mr. Obama's remarks, Deputy Prime Minister Kadri Jamil said in spite of the apparent halt to the military buildup, Syrian forces would remain on a high state of alert, and he said that Syria would retaliate against any attack.  Mr. Jamil said in the interview from Damascus with the Lebanon-based news channel Al-Mayadeen that Mr. Obama's reversal would damage U.S. prestige worldwide, calling it a "muddied political position."  U.S. ambassadors had fanned out across the Middle East as they tried to prod Arab leaders for backing. Ambassadors have shared with Middle Eastern allies the administration's case for intervening, including intelligence about intercepted communications which the U.S. says shows the Assad regime directed the chemical weapons attack.  The Arab League took the step of moving up a planned meeting by two days, agreeing to gather on Sunday as they considered the possibility of new U.S. military action in their region.  However, the delay also could provide time to assemble the international support and to cement a military alliance on Syria with France, which has signaled it is willing to join the U.S. Mr. Obama on Saturday spoke by telephone with French President Francois Hollande.  Regardless of the potential consequences, Mr. Obama said he looked forward to discussing the Syria crisis with Congress and brushed off a growing body of criticism over his handling of the 2 ½-year-old civil war.  "I have decided that the United States should take military action against Syrian regime targets," Mr. Obama said, appearing alongside Vice President Joe Biden. "While I believe I have the authority to carry out this military action without specific congressional authorization, I know that the country will be stronger if we take this course, and our actions will be even more effective. We should have this debate, because the issues are too big for business as usual."  Mr. Obama did not respond to a question about whether he would order military action even if Congress voted it down.  He said pursuing congressional approval will not diminish the effectiveness of U.S. action, which he said would be of "limited duration and scope."  Not acting in Syria could lead to an escalation of chemical-weapons use and increase national security threats to the U.S., he argued, and embolden others to resort to the use of weapons of mass destruction.  Mr. Obama's shift came as he faced mounting pressure from members of both parties to seek congressional authorization for military action, a procedure he advocated as a presidential candidate. More than 180 lawmakers signed letters urging him to do so in the case of Syria. Some lawmakers have said they oppose a military response, while others—including House Speaker John Boehner (R., Ohio), have demanded more information about any U.S. mission in advance of a presidential order.  Mr. Obama sent a letter to Congress Saturday night with proposed legislation that would grant him authorization to use U.S. military force in Syria "as he determines to be necessary and appropriate in connection with the use of chemical weapons or other weapons of mass destruction in the conflict."  Senate Majority Leader Harry Reid (D., Nev.) voiced his support for military action in Syria and said the Senate will vote on a resolution by the end of the week of Sept. 9.  But the request is unlikely to satisfy some critics of Mr. Obama's Syria policy who argue any military mission should include the removal of Mr. Assad, which the president has advocated for the past year. One of the challenges for Mr. Obama as he sells his plan to Americans is to explain how this military action fits into his administration's broader policy on the Syrian conflict. The White House has advocated a political rather than a military solution to the civil war, but now says it cannot allow the specific use of chemical weapons to go unanswered.  Senate Minority Leader Mitch McConnell (R., Ky.) welcomed Mr. Obama's decision Saturday. "The president's role as commander-in-chief is always strengthened when he enjoys the expressed support of the Congress," Mr. McConnell said in a statement.  Others, however, called the move a decided step back from a strenuous response to Syria.  "President Obama is abdicating his responsibility as commander-in-chief and undermining the authority of future presidents," said Rep. Pete King (R., N.Y.). "The president doesn't need 535 members of Congress to enforce his own red line."  The legislative effort is likely to consume a great deal of political energy and throws the issue open to debate over the scope and goals of the U.S. action. The Obama administration wants to conduct a limited military campaign to "deter and degrade" the country's chemical weapons capabilities.  GOP Sens. John McCain of Arizona and Lindsey Graham of South Carolina said they can't support such strikes because it won't significantly change momentum on the battlefield, where the Assad forces are locked in a standoff with rebels.  To work through such questions, Rep. Adam Schiff (D., Calif.) said the House should go back into session immediately.  Some GOP lawmakers questioned whether the White House was still resolved to act.  "I hope this is not a case of them having second thoughts and using Congress as a foil," said Sen. Bob Corker (R., Tenn.), the senior Republican on the Senate Foreign Relations Committee. Mr. Corker said he sought and received assurances from the White House that the president was fully committed to pursuing the military options.  Mr. Boehner applauded the move to seek congressional authorization, but said a House vote would take place the week of Sept. 9. "We are glad the president is seeking authorization for any military action in Syria in response to serious, substantive questions being raised," he said.  Top administration officials already were seeking to smooth over congressional concerns about a new military operation in the Middle East by briefing lawmakers on the underlying intelligence and strike planning.  Republican members of the House were notified Saturday in an email that administration officials delivered classified intelligence to the Capitol late Friday night for House members to review. Administration officials are also briefing Senate Democrats and Republicans Saturday afternoon about Syria, congressional officials said.  Write to Carol E. Lee at carol.lee@wsj.com and Adam Entous at adam.entous@wsj.com
The president said he is prepared to order military action against Syria, but said he would first seek approval from Congress before ordering any strikes.