Even as President Obama lays out his vision of America's obligations to civilians menaced by their own governments, the limits of what some are calling an "Obama Doctrine" are evident in his differing approaches to Libya and another Arab country in turmoil: Syria.
Ignoring Libyans in danger from Moammar Kadafi's forces "would have been a betrayal of who we are," the president said this week in defending the U.S.-supported air war there. Yet the administration has made it clear that the military option is not "on the table," in Syria, where dozens of protesters also have been killed.
A senior administration official confirmed that even milder measures, such as a tightening of U.S. sanctions, withdrawal of the ambassador to Syria, or other efforts at economic or diplomatic isolation are not being weighed.
Both countries are within reach of missiles and warplanes launched from U.S. ships in the Mediterranean. The difference in U.S. policy toward them is an example of Obama's general approach to government: seeing policy in shades of gray rather than black and white.
But the administration has struggled to explain why it has intervened in one country and not the other. The explanation is difficult in part because it has less to do with humanitarian issues than with harder calculations of national interest.
Obama indicated in his speech to the country Monday that Libya met a set of specific conditions for military action, including an international mandate, a broad coalition willing to take part and appeals from Libyans themselves. Rebels in eastern Libya quickly formed an alternative government and sought foreign intervention through establishment of a no-fly zone.
"I don't know if those circumstances could be duplicated anyplace else," Obama told ABC News on Tuesday. He added that in each case, he needed to measure the national and international interest, and the possibility of success versus the risks involved.
While the death toll has risen into the dozens in Syria, officials point out that it is still far lower than the thousands feared killed in Libya, and probably many fewer than would be needed to build foreign support for military intervention there.
"We're not anywhere near the kind of situation that drew all the international support for Libya," the senior official said.
Moreover, although Libya is a major oil producer, the strategic stakes are smaller than in Syria. And many more neighboring governments were fed up with Kadafi.
In Syria, U.S. officials worry that a collapse of the regime could lead to chaos that could destabilize neighboring Lebanon and increase the risk of war with Israel. They also fear that the secular dictatorship of President Bashar Assad could be replaced by an Islamist government. Adding to the problems, Syria has deep sectarian divisions, which could crack open if the government's grasp is weakened.
Israel, the top U.S. ally in the region, has been urging caution, worried about what a successor regime might look like. Though the Syrian regime has been one of Israel's most threatening adversaries, many Israelis consider it predictable.
Other U.S. allies share some of the same hesitations. A senior European diplomat predicted strong international resistance to any effort to organize international action against Syria.
"Also to be considered is the regime that would follow Assad," said the diplomat, who spoke on condition of anonymity because of the sensitivity of the subject.
At least some U.S. officials still cling to the hope that Assad's regime can help solve some of the most pressing problems in the Middle East. Many past administrations have held the same hope, only to be disappointed.
Notwithstanding deep skepticism in Congress, the Obama administration has been working since it took office to win Syria's cooperation in building an Arab-Israeli peace, containing Iran, and other Mideast projects.
Secretary of State Hillary Rodham Clinton made the administration's view clear recently when she described Assad as a "different leader" than his father, President Hafez Assad, who ordered the killing of thousands of Syrians to put down protests in 1982. Clinton implied that the younger Assad might become a reformer.
The opening to Syria was a sharp contrast with the policy of President George W. Bush, who made early attempts to cultivate Syria relations, then concluded that the regime would never cooperate, pulled the U.S. ambassador and added sanctions.
So far, the Obama administration's effort to court Syria has borne little fruit, a point hammered by Republican presidential hopefuls and conservative critics. Former Minnesota Gov. Tim Pawlenty said Clinton's suggestion that Assad might be a reformer was "either ignorant or frighteningly misguided."
Even some human rights activists who are often allies of the administration are urging it to increase pressure on Damascus.
Tom Malinowski, Washington director for Human Rights Watch, said Assad had shown definitively in a speech this week that he did not intend to carry out political reforms. "This should be a pivot point," he said.
The fundamental problem with the administration's approach, said Daniel Kurtzer, a former ambassador to Israel and an advisor to Obama in the 2008 election, is that "there isn't anything that really separates what's happening in Libya from what's happening in Syria — nothing at all."
The administration's attempt to separate the two policies "isn't going to work if people keep getting killed," he said.
Times staff writers Jeffrey Fleishman in Cairo and Borzou Daragahi in Tripoli, Libya, contributed to this report.