Eleven nations, including the United States, expelled Syrian diplomats Tuesday. But while that reaction to a continuing series of atrocities committed by President Bashar Assad’s government was thoroughly justified, it won’t dim his zeal for brutally suppressing a popular uprising that began in last year’s Arab Spring.

And while it has been easy to decry the barbarism of Assad’s forces over the last 14 months, it remains extremely difficult to craft an effective international response that will speed the end of his repressive, dynastic regime.

President Assad, like his father before him, aims to stop a mass rebellion with mass murder. According to the United Nations, more than 10,000 Syrians have been killed since the government launched its crackdown on protesters early last year.

Though former U.N. Secretary-General Kofi Annan brokered a “cease-fire” that began seven weeks ago, the carnage has continued.

A particularly grisly incident last week claimed the lives of more than 100 villagers in central Syria as a pro-government militia “summarily executed” men, women and children, according to U.N. monitors. And 13 bound corpses, also apparently victims of government killers, were discovered in eastern Syria Wednesday.

U.S. State Department spokeswoman Victoria Nuland dismissed the Syrian government’s attempts to deflect blame for last week’s atrocity, pointing out that “these were regime-sponsored thugs who went into villages, went into homes and killed children at point-blank range and their parents.”

That slaughter, along with the cease-fire’s utter failure, moved Mr. Annan to warn this week that the Syrian crisis has reached a “tipping point.”

Yet despite that dire assessment and widespread outrage from the world community, NATO clearly doesn’t have the stomach to intervene in Syria they way it did last year in Libya. Faced with a similar scenario as Col. Moammar Gadhafi turned his military on his people, NATO played a key role in the longtime Libyan dictator’s demise.

Col. Gadhafi didn’t just lose his power. Two months after fleeing from Tripoli, he lost his life.

However, Assad’s armed forces, including his air defenses, are far superior to those that failed Gadhafi. And during last week’s NATO summit in Chicago, the assembled world leaders were conspicuously silent on the ongoing bloodletting in Syria.

Another obstacle: Russian President Vladimir Putin continues to back Assad, refusing to go along with tougher U.N. resolutions and sanctions. Mr. Putin even sent the Syrian government more military supplies earlier this month.

And some international leaders, though deploring Assad’s tactics, are wary about the unpredictable aftermath of his potential downfall. As in Libya and Egypt, the transition to self-government in the Mideast can produce chaotic results.

So don’t count on Mr. Annan’s repeated appeals to Assad to stop the wholesale killing of civilians in Syria anytime soon.

Don’t count, either, on the optimistic notion that President Barack Obama can somehow persuade Mr. Putin, during the G-20 Summit in Mexico on June 18-19, to stop propping up Assad’s regime.

Unfortunately, the end to Syria’s agony doesn’t appear to be coming soon.

But that grim short-term reality doesn’t mean Assad’s government can survive over the long term as Syrians demand their freedom.

And though the international community hasn’t found a way to pry Assad from power, it must continue to condemn his savagery .

Responsible world leaders also must use all available pressure points to hasten the ouster of the tyrant — and the end of the Syrian people’s suffering.