Short of waging war alongside rebel forces to topple Libya's Moammar Gadhafi, international military options are limited to largely symbolic efforts, and all are fraught with risks ranging from failure to creating another quagmire for stretched-thin U.S. forces.
"There is a lot of, frankly, loose talk about some of these military options," an exasperated U.S. Defence Secretary Robert Gates said. "Let's just call a spade a spade; a no-fly zone begins with an attack on Libya to destroy the air defences. That's the way you do a no-fly zone. And then you can fly planes around the country and not worry about our guys being shot down."
Among those pushing for international forces to keep Libyan warplanes grounded are Britain's Prime Minister David Cameron, while U.S. Secretary of State Hilary Clinton said it was "under active consideration."
Military-intervention options range from a naval blockade, to a no-fly zone, to "decapitating" air strikes by U.S. warplanes, to a full-blown beachhead established by the U.S. Marines to supply and support the rebels. These and other ideas have been suggested by European politicians, various security experts and the nascent Libyan rebel government in rebel-held Benghazi.
Toppling the Taliban in Afghanistan with air strikes and Special Forces fighting alongside the Northern Alliance seemed an easy, almost casualty-free exercise a decade ago. But more than 100,000 U.S., Canadian and other Western forces remain in Afghanistan battling a raging counterinsurgency in which foreign troops - once seen as liberators - are widely regarded as unwelcome occupiers.
Any no-fly zone would need UN Security Council approval plus the backing of neighbouring Arab governments and would involve several hundred U.S. and allied warplanes flying from land bases in Italy and carriers in the Mediterranean. It might also be largely ineffective. U.S. and British warplanes enforced no-fly zones over northern and southern Iraq for more than a decade until ground forces toppled Saddam Hussein, but the Iraqi dictator's brutal rule was largely unaffected.
It might fail to tip the balance in favour of the rebels, especially if Colonel Gadhafi manages to retain the loyalty of even a few thousand well-equipped and ruthless troops.
"The UN Security Council resolution provides no authorization for the use of armed force," Mr. Gates pointedly noted. "There is no unanimity within NATO for the use of armed force."
China, a veto-wielding permanent member of the Security Council, is typically wary of setting precedents for international intervention in matters of national sovereignty, and is unlikely to authorize the use of foreign forces to back pro-democracy rebels against even the most brutal of regimes.
Even if advocates of military intervention managed to win Security Council endorsement - something that didn't happen before NATO launched an air war to drive the Yugoslav military out of the then-Serbian province of Kosovo - the scope of a no-fly order would be complex. Would it, for instance, allow for the shooting down of Col. Gadhafi's presidential jetliner believed to be flying mercenaries to Tripoli?
The spectre of Western military intervention to force regime change in the Arab world would also send shock waves across the region, not least among already nervous U.S. allies such as Saudi Arabia, which has already seen long-standing U.S. friend Hosni Mubarak abandoned in Egypt.
So far, the U.S. military moves have been modest - sending a pair of warships into the Mediterranean aimed to bolster humanitarian aid operations.
Mounting demands that something more be done were matched by differing views over what that should be.
James Dobbins, a veteran special envoy involved in U.S. military interventions in Afghanistan, Kosovo, Bosnia, Haiti and Somalia, and now director of the International Security and Defense Policy Center at the RAND Corp., offered this warning in Time magazine. "What we've learned over the last 20 years is that overthrowing objectionable governments is easy," Mr. Dobbins said. "Replacing them with something good is hard."