By LOLITA C. BALDOR
WASHINGTON (AP) -- Questions are already swirling about the endgame as the Obama administration prepares for a likely strike against Syria as punishment for an alleged chemical weapons attack in its civil war.
National security experts and some U.S. officials question whether a limited strike can have any lasting impact on Syrian President Bashar Assad, or whether it will simply harden Assad's resolve. And it's not clear how much the military operation could help the beleaguered and splintered Syrian opposition, or lessen concerns that hard-line rebels may not support America if they do seize control of the country.
A limited, short-term operation, however, may be a compromise between military leaders, who have warned against entering a civil war, and a White House determined to show that President Barack Obama meant it when he said last year that the use of chemical weapons would cross a red line.
The broader objective is to damage the Syrian government's military and weapons enough to make it difficult to conduct more chemical weapons attacks, and to make Assad think twice about using chemical weapons again.
Senior national security leaders met again at the White House on Tuesday as the administration moved closer to an almost certain attack on Syria in the coming days. The most likely military action would be to launch Tomahawk cruise missiles off U.S. warships in the Mediterranean Sea. The Navy last week moved a fourth destroyer into the eastern Mediterranean and it is expected that the British would also participate in an attack.
The looming military action has spurred debate over what the administration hopes to gain and whether a limited military campaign -- either several hours or a couple of days -- could do much to further the overall goal of ousting Assad from power or moving Syria toward a more democratic government. The administration says it isn't aiming that high in whatever action unfolds.
"The options we are considering are not about regime change," said White House spokesman Jay Carney.
Anthony Cordesman, a national security expert at the Center for Strategic and International Studies, is skeptical that U.S. action will make a lasting difference.
"You can impact targets that have political value and military value," he said. "But it doesn't shape the outcome or provide security for the people, and it certainly doesn't deter Assad from going on. At the end of it, it's a little more like winning a schoolyard fight than accomplishing anything of strategic meaning."
One of the more vocal critics is the top military officer, Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, who alluded to such concerns in a letter to Sen. Carl Levin, chairman of the Senate Armed Services Committee.
Dempsey said that military strikes could help the opposition and put pressure on Assad, but -- pointing to the last decade of war in Iraq and Afghanistan -- he added, "it is not enough to simply alter the balance of military power without careful consideration of what is necessary in order to preserve a functioning state."
And he warned that if the government collapses without a viable opposition to take its place, "we could inadvertently empower extremists or unleash the very chemical weapons we seek to control."
Dempsey said a limited operation could involve hundreds of missile strikes on Assad's air defense, weapons systems, military facilities and command headquarters and, depending on the duration and expanse of naval and air assets used, could cost billions.
Christopher Griffin, executive director of the Washington-based Foreign Policy Initiative, questioned the wisdom of conducting a limited operation to punish Assad.
"Any military action taken just to send a message would send the wrong message," said Griffin. "It would undermine the president's stated policy that Assad must go and the administration's stated intent to work with a moderate anti-Assad opposition."
He and others point to Obama's announcement some weeks ago that the U.S. would be sending a variety of weapons to help arm the Syrian rebels. To date, officials say no weapons have been delivered.
The military strikes, Griffin said, must be "part of a broader strategy to force Assad to go, to create a moderate opposition that we can work with, and to prepare for Syria's future."
Richard Haass, president of the Council on Foreign Relations, said providing "significant" arms to the rebels would be the best way to help shape the battlefield and influence the outcome in Syria.
"I think the strikes are in a narrow way successful by simply occurring," Haass said. "It shows that you cannot use these weapons and get off scot-free," said Haass. "If the Syrians continue to slaughter -- as I believe they probably would -- their fellow citizens as the civil war continues, then the United States has other means rather than direct military participation to counter that. And that's where I have been arguing, will continue to argue, for serious arming of the opposition."
Based on precedents and military procedures, the U.S. is likely to launch a barrage of missiles from the four destroyers that are out in the Mediterranean. The initial volleys could last hours, and would probably be followed by a period of assessment, as the U.S. uses satellites and other means to determine the impact of the strikes. At that point, the U.S. could launch another round or two of strikes, as it continues to evaluate progress.
The immediate worry, then, would be retaliation by Assad and the possibility that attacks could send thousands more Syrians flooding across the borders into Turkey and Jordan seeking refuge.
"If Bashar Assad didn't hesitate to use chemical weapons against his own sleeping civilians, what's to stop him from using them against sleeping Turks, Jordanians or Israelis?" asked Michael Rubin, senior fellow at the American Enterprise Institute.
"That's the nightmare scenario, which the United States and the Pentagon would be going through right now, in determining what we can do to stop that retaliation and what we would do if this conflict and chemical weapons cross international borders."
In the broadest policy terms, however, officials and observers agree that the U.S. has little choice but to respond in some way.
Obama has said the use of chemical weapons would cross a "red line," suggesting it would trigger U.S. intervention in the bloody, two-year civil war. Over the past several days, top administration officials, including Secretary of State John Kerry and Vice President Joe Biden, have said they have little or no doubt that the government used chemical weapons in an attack outside Damascus last week.
Anti-government activists in Syria and Doctors Without Borders say that more than 300 people were killed in an artillery barrage by government forces Wednesday that they say included the use of toxic gas. The government calls the allegations "absolutely baseless."
That episode follows other suspected chemical weapons attacks on a small scale earlier this year.
"President Obama issued those words - red line - a little more than a year ago," said Rubin. "If you draw a line in the sand and you allow your opponent to cross, then that's not an issue of confidence only in Syria, but that's something the North Koreans will be watching, the Iranians will be watching and potentially other rogues around the globes will be watching. So the whole idea of a symbolic strike is to say `you can't cross the line.'"
AP Broadcast reporter Sagar Meghani and AP writer Deb Riechmann contributed to this report.