The most likely U.S. military action would be to launch Tomahawk cruise missiles off U.S. warships in the Mediterranean. The Navy last week moved a fourth destroyer into the eastern Mediterranean.
Officials said it was likely the targets would be tied to the regime's ability to launch chemical weapons attacks. Possible targets would include weapons arsenals, command and control centers, radar and communications facilities, and other military headquarters. Less likely was a strike on a chemical weapons site because of the risk of releasing toxic gases.
Military experts and U.S. officials on Monday said that the precision strikes would probably come during the night and target key military sites.
The president has ruled out putting American troops on the ground in Syria and officials say they also are not considering setting up a unilateral no-fly zone.
On Capitol Hill, bipartisan support for a military response appeared to be building.
Rep. Adam Schiff, a California Democrat on the House Intelligence Committee, backed the idea of targeted strikes against key Syrian infrastructure, saying it would both be a deterrent to future use and carry "less risk of drawing us in further, or spreading the conflict."
Republican Sen. Bob Corker of Tennessee said he would support "a surgical, proportional strike" against the Assad regime, but called on the administration to seek congressional authorization for such actions.
It's unlikely that the U.S. would launch a strike against Syria while the United Nations team is still in the country. The administration may also try to time any strike around Obama's travel schedule — he's due to hold meetings in Sweden and Russia next week — in order to avoid having the commander in chief abroad when the U.S. launches military action.
U.N. Secretary-General Ban Ki-moon on Monday countered the U.S. claim that the investigation at the site of last week's attack was too little, too late.
"Despite the passage of a number of days, the secretary-general is confident that the team will be able to obtain and analyze evidence relevant for its investigation of the August 21 incident," U.N. spokesman Farhan Haq said in New York