Washington - The United States has ruled out unilateral military action against Syria and is conferring with allies on potential punitive strikes that could last for more than a day, a senior US official said on Wednesday.
"Any military action would not be unilateral. It would include international partners," the senior administration official, who spoke on condition of anonymity, told reporters.
The strikes against Syria, if ordered, could extend beyond a single day, the official said.
"The options are not limited just to one day."
Amid speculation Britain and France would join in the possible strikes, US officials declined to comment on whether the military action under consideration would go beyond the use of cruise missiles and require fighter aircraft to enter Syrian airspace.
"We're exploring every option," the official said.
The official's comments offered the latest sign President Barack Obama and US allies were moving towards military action against Syria over its alleged use of chemical weapons.
Obama's deputies were holding discussions with Turkey, Jordan and other partners on contingency plans in preparation for any retaliation by the Syrian regime in the event of US-led action, the official said.
Washington was looking at "what could likely be the reaction, the consequences" of military action.
"There's a possibility that the Syrian government would use chemical weapons again. I don't think you can discount that," said the official.
But if the United States took no military action against Damascus, then it would send a dangerous signal to other regimes with chemical stockpiles, including North Korea, the official said.
Citing North Korea, the official said "what's to say, as they [the North Koreans] watch this play out in Syria, they wouldn't use weapons like this?"
Obama's aides were still working to define the precise objective of any potential intervention, a second administration official said.
The purpose of the strikes would likely be aimed at deterring President Bashar Assad's regime from using chemical weapons again and degrading its ability to do so, the second official said.
The Assad regime has warned Washington against intervention but the United States was prepared for possible retaliatory action from Syria or its allies, according to the second official.
"We believe we can manage any Syrian reprisals" or reaction from "outside players," including Iran or Hezbollah militants in Lebanon, he said.