"The options are not limited to just one day," the official said, speaking on condition of anonymity, as the prospects for a U.S.-led air and missile assault on Syria looked all but certain.
Though the White House said President Barack Obama had yet to make a final decision on exactly how to respond, U.S. security officials have said that any air campaign would likely involve cruise missiles fired from U.S. warships in the Mediterranean.
But the United States does not intend to act unilaterally should it choose to go forward with military action, the senior official said. "We're talking to a number of different allies regarding participation," the official said.
Obama, who has long been wary of any intervention in Syria's civil war, has been consulting allied leaders to lay the groundwork for action aimed at punishing Syrian President Bashar al-Assad's government for last Wednesday's gas attack near Damascus.
U.S. intelligence agencies were assembling what they are sure to say is final confirmation of the Syrian government's culpability for the chemical weapons attack, and the White House said their report would be completed this week. Assad's government has denied responsibility.
A second administration official said the United States was still defining its objectives but that strikes to deter Assad from using chemical weapons in the future and degrade his ability to do so were under consideration.
White House spokesman Jay Carney said on Tuesday that a U.S. response would not have the goal of "regime change" in Syria, suggesting that Obama remains cautious about getting too deeply involved in the conflict. Polls show most Americans oppose U.S. intervention.
Republican U.S. Senator John McCain, a harsh critic of Obama's Syria policy, rejected that limited goal.
"This conflict cannot be contained within Syria, and we have to understand that and that's why we've got to help these people get rid of Bashar al-Assad, to get the momentum back on their side," he said on MSNBC. (Reuters)
