Five months after President Barack Obama told him to leave Libya, Moammar Gadhafi is pressing on against NATO-backed rebel forces, flaunting his remaining power in the face of Western nations fearful of combatting him with greater force. And four months after Obama offered Syria's leader an ultimatum to lead reform or leave, Bashar Assad's crackdown on dissent rages on.

Through intervention or engagement, the U.S. is stuck with inconclusive results in both countries. And while American officials are loath to compare the civil war in Libya to the civil unrest in Syria, they say neither conflict makes for easy solutions. The unclear endgame in each is constraining the actions of everyone involved — including the United States.

Coming out with guns blazing failed to deliver an early knockout punch to Gadhafi, who seems determined to prolong four decades of crafty and often cynical rule that has seen him crush all previous attempts at liberalization. Engagement has proved similarly ineffectual directed toward Assad, who has mixed promises of reform and symbolic steps toward greater democracy with fierce repression, leaving much of his country in a state of siege.

Libya's war has become a quagmire. On Thursday, rebel commander Abdel-Fattah Younis was shot and killed under mysterious circumstances, just before arriving for questioning by opposition authorities over alleged family links to the Gadhafi regime. His death raised the specter of a troubling split within the rebel movement at a time when their forces have failed to make battlefield gains despite NATO's pounding airstrikes on Gadhafi's military.

The killing also underlined the uncertainty of the war. The United States and several dozen other nations have recognized the rebel leadership as Libya's legitimate rulers, but Gadhafi had held onto a large part of the country. The government's grip on the capital, Tripoli, seems secure.

Younis' death is unlikely to lead the U.S. and its allies into any abrupt change in their decision to throw their weight behind the rebels in Libya's civil war. It could, however, show signs that the movement is imploding or turning against its own, with much of the work of ousting Gadhafi still unachieved. And it casts doubt on the repeated claims in Western capitals that the rebels have proved themselves worthy national leaders and that Gadhafi's regime is on the verge of collapse.

For the U.S., policy options are limited. It has already played its military card, leading the early stages of NATO's intervention by bombing Gadhafi's air defense capabilities. Since then it has played a more auxiliary role in the alliance, pitching in with plane refueling, reconnaissance and some drone strikes. And there is fierce resistance from Congress to ramping up U.S. aerial attacks anew.

Politically, meanwhile, the oft-repeated U.S. demand that Gadhafi must leave power and leave Libya has left the Obama administration with little wiggle room for a creative diplomatic solution.

American officials met with Gadhafi representatives earlier this month, but insisted that they didn't hold a negotiating session. Instead, officials said they pressed the administration's commitment to seeing Libya's leader end his rule. The meeting apparently produced no concrete results and officials said they had no plans to meet with regime officials again.

In Syria, the president and Secretary of State Hillary Rodham Clinton have hardened their rhetoric in recent months. It appears they've dismissed any lingering hopes that Assad's government might be persuaded to start a serious democratic reform process and pull back his security forces from an aggressive nationwide campaign to snuff out dissent.

Obama has promised to use "all the diplomatic, economic and strategic tools" available to support democratic transition. Yet it's unclear what effect the pressure is having, or how big a toolbox is at the administration's disposal. The president specifically left out any military options.

Activists say more than 1,600 civilians have died since protests erupted in mid-March and daily reports of deaths in demonstrations are adding to the Syrian toll. The government blames the unrest on terrorists and foreign extremists, and shows little signs of backing down.

Testifying this week before a House foreign affairs subcommittee, the State Department's top human rights official, Michael Posner, repeated the administration's mantra that Assad has acted barbarically, lost legitimacy and placed himself on the wrong side of history. But pressed by lawmakers to explicitly call for regime change in Syria, he demurred.

Jeffrey Feltman, the top U.S. diplomat for the Middle East, added that the U.S. was limited in what economic force it could apply. "We start from the reality that Syria is one of the most sanctioned countries in the world when it comes to trade and relations with the United States," he noted, saying officials were asking European nations to enact oil, gas and other sanctions against Assad's regime.

And as for the limited engagement with Syria's regime that remains, the administration has struggled to say how it has tempered the government crackdown or accelerated an end to the repression. The U.S. has little capacity to threaten further isolation or economic punishment of Assad's often anti-American and pro-Iranian government — unlike in Egypt, where Obama was able to help usher long-time ally Hosni Mubarak out of power.

Posner said the U.S. ambassador to Syria, Robert Ford, was "greeted as a hero" when he went to the restive city of Hama earlier this month, a trip designed to demonstrate U.S. solidarity with demonstrators. That may have provided some moral fortitude to those braving the streets in protest, but the violence continues.

What Ford or any other American official has been able to say — or do — to have a real effect in Syria is unknown. On several occasions, Ford's requests to even speak with senior Syrian officials have been denied.