President Barack Obama said on Saturday he had decided the United States should strike Syrian government targets in response to a deadly chemical weapons attack, but said he would seek a congressional vote for any military action.
Waiting for congressional approval essentially means an attack would wait until Congress returns to session on September 9.
"We cannot and will not turn a blind eye to what happened in Damascus," Obama said in statement at the White House Rose Garden.
The president challenged lawmakers to consider "what message will we send to a dictator" if he is allowed to killed hundreds of children with chemical weapons without suffering any retaliation.
Obama's decision likely delays US action for at least 10 days.
In a statement from the White House Rose Garden, US president said he had authorized the use of military force to punish Syria for a chemical weapons attack on August 21 that US officials say killed 1,429 people. Military assets to carry out a strike are in place and ready to move on his order, he said.
But in an acknowledgement of protests from US lawmakers and concerns from war-weary Americans, Obama added an important caveat: he wants Congress to approve.
"Today I'm asking Congress to send a message to the world that we are ready to move as one nation," Obama said.
Obama's decision was a big gamble that he can gain approval from Congress in order to launch a limited strike against Syria to safeguard an international ban on chemical weapons usage, guard US national security interests and protect regional allies like Turkey, Jordan and Israel.
"I have long believed that our power is rooted not just in our military might, but in our example as a government of the people, by the people, and for the people," Obama said.
His decision was also a significant shift away from what was perceived to be a strike fairly soon against Syrian targets. He had been prepared to act unilaterally after the British parliament refused to go along with American plans.
Protracted and expensive wars in Afghanistan and Iraq have left Americans reluctant to get involved in Middle Eastern conflicts.
Most Americans do not want the United States to intervene in Syria. A Reuters/Ipsos poll taken this week showed only 20% believe the United States should take action, but that was up from 9% last week.
A debate has raged for days in Washington among members of the US Congress over whether, or how quickly, Obama should take action.
Senate Republican leader Mitch McConnell backed the move, which he said Obama had told him about.
"The president's role as commander in chief is always strengthened when he enjoys the expressed support of the Congress," said McConnell.
Obama's decision was announced after he met his national security team at the White House. Top aides were to brief senators later in the day and members of the House of Representatives are to receive a classified briefing from administration officials on Sunday.
The objective is to show solid proof that US intelligence officials say shows conclusively that the Syrian government of Syrian President Bashar Assad launched a large chemical weapons assault in Damascus suburbs that left among the dead 426 children.
Obama has broad legal powers to take military action, and he insisted he felt he had the authority to launch a strike on his own. But he said he wanted Congress to have its say.
The Lebanese newspaper Al Diyar reported Saturday that Syrian President Bashar Assad was in an underground war room in an unknown location. According to the Lebanese report, he was with his work team, which includes military officers.
Additionally, the report claimed that his wife and children were in a safe location as well. Other senior Syrian regime officials are reported to have sent their families to safe, apparently underground locations.
UN inspectors arrived in Amsterdam after spending several days in Syria collecting soil samples and interviewing victims of an attack last week in the Damascus suburbs. Officials said it could me more than a week before their final report is complete.
It seemed unlikely Obama would wait that long to order any strike, given the flotilla of US warships equipped with cruise missiles and massed in the Mediterranean; Friday's release of a declassified US intelligence assessment saying Assad's chemical weapons killed 1,429 civilians; and an intensifying round of briefings for lawmakers clamoring for information.
The president said Friday that he was considering "limited and narrow" steps to punish Assad for the attack, adding that US national security interests were at stake. He pledged no US combat troops on the ground in Syria, where a civil war has claimed more than 100,000 civilian lives.
With Obama struggling to gain international backing for a strike, Russian President Vladimir Putin urged him to reconsider his plans, saying he speaking to him not as a president but as the recipient of a Nobel Peace Prize.
"We have to remember what has happened in the last decades, how many times the United States has been the initiator of armed conflict in different regions of the world, said Putin, a strong ally of Assad. "Did this resolve even one problem?"