Washington ? 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.

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.

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.