And the Syrian horror goes on as Russia and China block another Security Council resolution

Only incurable optimists would count on United Nations sanctions rapidly toppling the mass-murdering regime of Syrian President Barshar Assad.

But if Russia and China had not vetoed a Security Council resolution with that sanctions threat Thursday, the U.N. could have at least delivered justified international condemnation of Mr. Assad’s bloody attempt to suppress a popular rebellion.

President Barack Obama’s Wednesday night call to Russian President Vladimir Putin evidently failed to make him see that Mr. Assad must go. Russia and China both do lots of business with Syria — and are both wary of what would come next if the government falls.

Yet while Mideast power changes are fraught with peril, at this tragic point, such a change must be made in Syria. The savage nature of the Assad dynasty has been re-confirmed over the last 16 months.

So has the firm Arab Spring resolve of the Syrian people to free themselves from it .

And so has the futility of the U.N. in this crisis.

Former U.N. Secretary General Kofi Annan led a joint U.N.-Arab League effort to bring peace to Syria. But despite an April “cease-fire” unworthy of that title, Syrian forces have continued their slaughter of not just rebels but non-combatant civilians.

The scheduled mission of the U.N. observers who have documented so many government atrocities over the last few months is due to end today.

According to a general consensus, at least 14,000 people have been killed since the start of the rebellion.

But it was Wednesday’s loss of life among Mr. Assad’s dwindling loyalists that drew protests from Russian and Chinese diplomats.

A rebel bomb attack in Damascus killed three top Syrian defense officials, including Gen. Assef Shawkat, Mr. Assad’s brother-in-law. Russian Foreign Minister Sergey Lavrov, citing that assault, accused the U.S. and other Western nations of “inciting” more violence.

Now we know what it takes for Russian officials to finally speak out against the mayhem in Syria.

Fierce fighting continued Thursday in Damascus, with rebel forces reportedly holding their own. Meanwhile, thousands more Syrians fled into Lebanon, just as many have fled in past weeks into Turkey.

As U.S. Defense Secretary Leon Panetta aptly put it, the situation in Syria is “rapidly spinning out of control,” requiring “maximum pressure” from the international community on Mr. Assad to step down.

Too bad that pressure is sadly lacking. Thursday’s U.N. inaction marked the third time since the uprising began that Russia and China have vetoed a Security Council resolution against Syria.

Susan Rice, U.S. ambassador to the United Nations, told the council after the vote: “The first two vetoes were very destructive. This veto is even more dangerous and deplorable.”

Amb. Rice added that the U.S. would no longer “pin its policy” on unarmed U.N. observers who didn’t have even “minimal support” from the Security Council. Instead, she said America would seek new coalitions to bring pressure on the Assad government.

And despite Thursday’s setback, such efforts to galvanize global opposition against Mr. Assad’s brutal tyranny must continue.