Shocking as it was, the massacre of more than 100 Syrian villagers is unlikely to galvanize a military assault like last year's campaign in Libya to oust Moammar Gadhafi. The killings, however, did provoke the strongest international condemnation the United States and other nations could muster.

The U.S. joined more than a dozen nations in expelling Syrian diplomats on Tuesday, and Republican presidential candidate Mitt Romney pushed for further, direct action to dislodge Syrian President Bashar Assad. But President Barack Obama's spokesman emphasized more limited options.

"We do not believe that militarization, further militarization of the situation in Syria at this point is the right course of action," said White House press secretary Jay Carney. "We believe that it would lead to greater chaos, greater carnage."

The nation's top military officer, Joint Chiefs of Staff Chairman Gen. Martin Dempsey, had appeared to hint at a possible shift in that longstanding U.S. position, saying Monday that despite reservations about military intervention "it may come to a point with Syria," because of the mounting atrocities.

Pentagon spokesman George Little said Tuesday that those remarks did not mean the United States had backed off its position that military intervention risks doing more harm than good. The Pentagon has not been asked to provide plans for military options in Syria, Little said.

"The focus remains on the diplomatic and economic track," Little said. "But at the end of the day, we in the Department of Defense have a responsibility to look at the full spectrum of options and to make them available if they're requested."

Romney, who is opposing Obama in this year's presidential election, said the massacre argued for strong action, including arming the rebels and pressuring Russia to stop selling arms to Assad forces.

"President Obama's lack of leadership has resulted in a policy of paralysis that has watched Assad slaughter 10,000 individuals," Romney said.

The administration's position reflects deep doubt that any bombing campaign could be accomplished quickly and relatively bloodlessly, as in Libya. The United States would have to be a major participant in any sustained coalition war to remove Assad, something U.S. officials had all but ruled out before the massacre in Houla over the weekend.

The United States is providing "non-lethal" assistance to the Syrian rebels fighting Assad, meaning supplies and help that do not include ammunition or weapons.

"Right now, our focus is on humanitarian aid, non-lethal aid, and I'm not going to speculate as to where the future might take us," Little said.

The administration is also helping other nations who are providing lethal aid determine suitable recipients.

"We and many nations that are _ that consider themselves friends of Syria _ are assessing the opposition as we help _ help them stand themselves up and help them unify," Carney said.

A senior U.S. official said events like this weekend's killings have the potential to provide a major change in an already perilous situation, and that the U.S. would seek to further move other nations toward a political solution due to the broad outrage over the killings and widespread fears that the window for a political solution is narrowing.

The chairman of the House Foreign Affairs Committee said the expulsion of the Syrian diplomat doesn't go far enough. Rep. Ileana Ros-Lehtinen said the U.S. should expel other Syrian officials and "expand our overall sanctions against Damascus."

Under pressure from lawmakers to do more, the White House is working to draft the legal framework for potentially wider U.S. engagement, two officials told The Associated Press. The scope of the authority was not clear, and White House officials would not confirm or comment on it.

"This is a political measure. This is a statement of our extreme disapproval and horror at the massacre," State Department spokeswoman Victoria Nuland said after Washington informed the top-ranked Syrian diplomat that he had 72 hours to leave the country. "We will obviously continue to look at other ways we can pressure the regime economically, politically, diplomatically, and continue to try to tighten the noose."

Carney also said the U.S. is working with allies to assess further action, but he gave no detail about what those next steps might include.

He threw cold water on efforts by Persian Gulf nations and some Republican critics to begin sending U.S. weaponry to the Syrian rebel forces, although he acknowledged that other nations may go ahead without U.S. help. The United States is worried that weapons would go astray and strengthen an Islamist terrorist movement or feed a possible civil war. Military officials also worry that even with additional arms the rebels would be hopelessly overmatched by Assad's army and the shabiha, the pro-government gunmen believed to be responsible for the Houla carnage.

"The nature and shape of and the membership of the opposition is still something that we and our partners are assessing," Carney said. "That is another consideration that has to be acknowledged when efforts like that are undertaken."

U.N. envoy Kofi Annan called the massacre a "tipping point," and the diplomatic deep freeze was swift.

"This amounts to abandoning all reason, sense, conscience, intelligence and mercy," Turkish Prime Minister Recep Tayyip Erdogan said Tuesday. "This inhuman massacre amounts to trampling all values that make a human being a human being."

The U.N.'s human rights office said Tuesday that most of the 108 victims in the town of Houla were shot at close range, including 34 women and 49 children, and entire families gunned down in their own homes. The expulsion of diplomats was a sign of "absolute disgust" with Assad's rule, the Obama administration said.

The United States will keep up pressure at the United Nations Security Council, and individually with allies and partners, Nuland said.

A lobbying effort with Syrian ally Russia is part of that effort. Russia has blocked U.S. efforts to impose a U.N. arms embargo or international travel ban for senior Syrian officials.

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Associated Press writers Julie Pace, Pauline Jelinek, Kimberly Dozier and Matthew Lee in Washington and Chris Torchia in Istanbul contributed to this report.