Syria's downward spiral

Reports that Russia is supplying Syrian President Bashar Assad with attack helicopters for use against rebel fighters and civilian protesters mark an ominous new phase in the country's descent into chaos and civil war. Mr. Assad's escalation from tanks and heavy artillery to aerial assaults threatens to spark a new arms race between the government and its opponents that can only lead to more bloodshed and suffering as long as he remains in power.

On Tuesday U.S. Secretary of State Hillary Clinton publicly took Russia to task for its role in fomenting the violence that has killed more than 10,000 Syrian civilians since the uprising began last year. Ms. Clinton rightly dismissed Russia's claim that the weapons it is sending Mr. Assad are purely defensive in nature. What other use could they have at this point except to attack Mr. Assad's own citizens?

It's inevitable that the rebels of the Free Syrian Army will now seek more potent weapons of their own to counter the government's helicopter assaults, which U.N. monitors have already observed targeting rebel strong points in recent days. The weapons of choice against attack helicopters are shoulder-fired surface-to-air missiles, delivered through Turkey and bankrolled by Saudi Arabia and Qatar, which up to now have been cooperating closely to get anti-tank rockets into rebel hands.

The effectiveness of those weapons in the narrow streets and alleys of rebel-held towns and villages forced Mr. Assad to switch strategies from tanks to attack helicopters. But giving the rebels shoulder-fired SAMs isn't something the U.S. and its allies should rush into. Since we don't know all the groups that make up the Syrian opposition, or their motives, there's no way to assure none of those weapons would fall into terrorists' hands, where they could be used to attack civilian airliners. That's a risk no one should be willing to take.

The UN's top peacekeeping official acknowledged on Tuesday what has been evident for some time now: The Syrian uprising has morphed from its beginnings in peaceful protests last year into a full-fledged civil war driven by sectarian violence. For all practical purposes, the peace initiative led by former U.N. Secretary General Kofi Annan is dead. Mr. Assad has made it abundantly clear that he has no interest in a negotiated settlement with his opponents leading to a transfer of power. Secretary Clinton acknowledged as much this week when she said U.N. monitors should leave the country by mid-July if there's no further progress toward a cease-fire.

That leaves the increasing likely prospect that the conflict may devolve into a proxy war that draws in Syria's neighbors as well as outside powers including the U.S., Russia and the European Union. Mr. Assad is desperate to maintain his grip on power and he has demonstrated a willingness to slaughter as many of his own citizens as necessary to achieve that end. But American officials are right to recognize that while the U.S. needs to keep engaging the international community on behalf of the Assad regime's victims, there may be little it can do to stop the killing, at least over the short term. A military intervention there simply is not a feasible alternative, and a rush to supply the rebels with the kind of sophisticated weaponry that would give them a shot at defeating their opponents could easily create more problems than it solves.