President Barack Obama's decision to seek congressional authorization is likely to delay any military strike against Syria by weeks, with possible repercussions for U.S. targets, for Syrian forces and for rebels.
However, U.S. defense officials said Saturday that they will be ready to go whenever a presidential order is given.
Defense experts struggled to find a precedent for a sudden pullback from a publicly telegraphed strike at the final moments. But U.S. officials said the situation wasn't unlike the 1990-91 Gulf War, where the U.S. had both a congressional debate and a long military buildup before pushing Saddam Hussein's forces out of Kuwait.
Still, the delay could endanger Syrian rebels, who were massing in some areas in order to take military advantage of U.S. strikes, analysts said. Mr. Obama's decision to delay a strike could allow Mr. Assad to attack those forces, said Christopher Harmer, a former Naval officer now with the Institute for the Study of War.
"He has given Bashar al-Assad a huge window to exploit the situation," Mr. Harmer said. "It is the best of all situations for Bashar al-Assad, it is the worst situation to the rebels."
Mr. Obama's decision also gives Mr. Assad time to move his forces around to try to minimize the military impact of any American strikes.
U.S. defense officials have worried that prolonged debate and discussions of potential targets have allowed Mr. Assad to begin dispersing elements of his military. Military analysts said the delay may be used to great advantage by Mr. Assad, and could have implications for whether chemical weapons fall into hands of militant groups. U.S. and Israeli officials have long worried about the possibility Mr. Assad could transfer chemical weapons to Lebanon's Hezbollah.
"We are seeing human shields get moved into place, units get moved, and all sides will try to change the situation on the ground," said Frederick Kagan, a military analyst at the American Enterprise Institute who has been critical of the Obama administration.
Defense officials said Saturday that while the delay caused by the congressional debate will pose a complication, U.S. intelligence and military experts will be able to find any targets that the Assad regime may attempt to hide.
"Our forces are poised and ready," said Air Force Col. Ed Thomas, a spokesman for Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff. "We can strike targets within Syria anytime the president directs."
Col. Thomas said the U.S. continues to refine its targeting based on the most recent intelligence.
Nora Bensahel, a scholar at Center for a New American Security, a think tank that has had ties to the administration, said most of the targets being considered by the military are "command and control" sites--structures that cannot easily be moved around by the Assad regime.
"The delay won't affect the target set significantly," she said.
George Little, the Pentagon press secretary, said that Defense Secretary Chuck Hagel supported Mr. Obama's decision to seek congressional approval for any attack on Syria.
Mr. Obama said Saturday that military strikes would be limited in "duration and scope" and designed to "hold the Assad regime accountable for their use of chemical weapons, deter this kind of behavior, and degrade their capacity to carry it out."
The president added that the Chairman of the Joint Chiefs of Staff "has indicated to me that our capacity to execute this mission is not time-sensitive; it will be effective tomorrow, or next week, or one month from now."
U.S. officials have said the strikes would be carried out by five Navy destroyers in the Mediterranean, the USS Mahan, Barry, Gravely, Ramage and Stout. All are armed with Tomahawk cruise missiles.
The Tomahawks have a range of 920 miles, meaning that the Navy ships can range throughout the eastern Mediterranean and still be in range to strike Syria.
The current leading option is for two days of strikes. But officials said that plan could change in the days to come.
Defense officials would not put a price tag on such a limited campaign but said it would not cost the billions of dollars that other military options have been assessed at.
"It's not cheap, but it's not Iraq," said a defense official. "The U.S. can afford whatever military action is taken."
U.S. officials have said the point of the strikes is to let Mr. Assad and other regimes know that the use of chemical weapons will come at a cost. A U.S. official said if the U.S. strikes Syria and the regime uses chemical weapons again, the military response is likely to be even greater.
"It is not that we will punch them in the nose and run away," the defense official said. "We will punch them in the nose and ask, 'Do you want more?'"
Mr. Kagan said the delay in the strike is unlikely to make a difference to U.S. objectives.
"If the goal is to simply demonstrate our displeasure, it hardly matters when we do it. There will always be something to hit," Mr. Kagan said.