WASHINGTON (Reuters) - President Barack Obama is gambling that his administration's failure to act forcefully to stem the bloody crisis in Syria won't become an election-year liability - and that looks for now like a good bet, with Americans weary of war and focused on the struggling U.S. economy.
A weekend massacre of civilians in Syria has again laid bare the lack of appetite on the part of Washington and many of its allies for military action against Syrian President Bashar al Assad.
It has also given presumptive Republican presidential nominee Mitt Romney a new opening to try to paint Obama as soft on U.S. foes and timid in asserting American global leadership.
But with most Americans opposed to another large-scale U.S. military commitment overseas and the Syria crisis barely registering for many U.S. voters, Obama's aides and supporters believe he can weather attacks on the issue.
Polls in recent months have shown between two-thirds and three-quarters of voters opposed to U.S. intervention. Not even human rights groups are demanding major military action.
And Republicans themselves are divided on the right course of action in Syria and how much political capital Washington should invest there.
"Americans are war-weary, Americans are focused on our own economy, Americans want us to invest in our future," Democratic U.S. Senator Mark Udall said in a conference call with reporters during a trip to the Middle East. "I don't think this is at the top of Americans' list of concerns."
Obama and his White House aides say they have limited options in the Syria crisis.
Efforts to persuade Russia to halt arms shipments to its long-time ally in Damascus and to get both Moscow and Beijing to drop their opposition to further U.N. sanctions have proven fruitless.
Obama for now has all but ruled out arming Syrian rebels, whose peaceful protests have morphed into a to-the-death fight over the country's future.
Romney has called for arming Syrian opposition groups. But even some of his fellow Republicans question the idea.
"We're just not exactly sure who the bad guys are and who the good guys are right now in Syria," the Republican chair of the House Intelligence Committee, Mike Rogers, said on Wednesday.
The Obama administration has also shown little appetite for imposing a "no-fly" zone over Syria and bombing Assad's loyalists to protect civilians - as was done by NATO in Libya last year - or carving out a humanitarian zone on Syria's borders under armed international protection.
In theory, at least, Obama could forge a coalition of willing countries - including some Gulf states and some NATO members - to oust Assad by force.
But the White House has made clear there is almost no chance Obama will do that. He his campaigning for reelection in November in part on his ending of one war, in Iraq, and winding down another, in Afghanistan.
In response to the massacre of 108 civilians in the Syrian town of Houla, Washington joined with its allies on Tuesday in the largely symbolic step of expelling Syria's envoys.
Romney, neck-and-neck with Obama in recent polls, seized the chance after the massacre to accuse the administration of a "policy of paralysis" on Syria, and Republican Senator John McCain called Obama's approach "feckless."
McCain has called for the U.S. to lead an international effort to protect key population centers in Syria through air strikes.
Yet except for calling for "more assertive measures to end the Assad regime" and for the United States to work with partners to arm the opposition, Romney has yet to present a detailed plan of his own.
Other Republicans' calls for action have tended to stop short of demanding U.S. military intervention, as for example House Foreign Affairs Committee chairwoman Ileana Ros-Lehtinen's statement on Tuesday that the United States should "expand our overall sanctions against Damascus."
Obama's aides believe he can weather political attacks over Syria, and that he is shielded on national security issues by his having ordered the killing of al Qaeda leader Osama bin Laden last year.
An Obama campaign official, responding to Romney's criticism on Syria, dismissed the former Massachusetts governor's ideas as "reckless and backward-looking."
The risk to Obama is a Syrian crisis that worsens further, destabilizes the region and gains traction with the American public. A U.N.-brokered ceasefire plan has all but collapsed, and diplomats admit there is no "Plan B."
That, plus continuing nuclear standoffs with Iran and North Korea, could give Republicans hope for putting Obama on the defensive over foreign policy - as they have done already with his economic stewardship.
Still, Republicans will have a tough time convincing many Americans of the need to wade further into Syria's troubles after more than a decade of costly wars.
"There is a clear disinclination of Americans to get involved in another military conflict in another far-off place," said Brian Katulis, a Middle East expert at the Center for American Progress think-tank in Washington. "It's a hard case to move forward and that will be the Republicans' burden."
In the meantime, the Obama administration is looking for other ways to tighten the screws on Assad.
Obama will meet Russian President Vladimir Putin during the June 18-19 G20 summit in Mexico.
Putin has shown little sign of budging from his opposition to tougher measures against Assad, but Obama is likely to press his case that the Syrian leader be eased out of power in a way modeled after the political transition in Yemen.
The White House may also have left the door open to U.S. acquiescence to allies vetting Syrian opposition fighters to see whether they are suitable for military assistance. "We can't speak for other nations and we can't prevent other nations from taking actions that are different from ours," White House spokesman Jay Carney said on Tuesday.
Additional reporting by Susan Cornwell and Jeff Mason; Editing by David Brunnstrom