Obviously, there will be risks. As in Libya, MANPADs and other weapons could get into the wrong hands. But that risk must be measured against the alternatives. The possibility that Syria will dissolve into a fractured land dominated by radical Sunni Islamists, perhaps confronting a rump Alawite bastion still led by Assad or his cronies, has already raised anxieties and altered calculations around the region. The conflict is also spilling over into Lebanon -- Syrian rebels claim to have been attacked by Hezbollah, and are threatening to retaliate against the Shiite militant organization's positions in Lebanon. And if a radical Sunni successor regime in Damascus inspires a return to Sunni-Shiite civil war in Iraq, then Iran is likely to cement its role in charting Iraq's future. Sectarian relations around the region -- in Bahrain, Saudi Arabia, and Lebanon -- will suffer, raising tensions and injecting additional instability into the equation.
A more moderate replacement for the Assad regime, on the other hand, would represent a blow to Iran and a boon to the United States and its regional partners and allies. Israel would be a primary beneficiary, with its antagonist, Hezbollah, having been dealt a serious setback. This, in turn, could enhance the prospects for peace with the Palestinian Authority.
To protect American interests, the Obama administration need not embark on a daunting, boots-on-the-ground engagement in Syria. However, it is time for the White House to signal clearly that it is ready to reconsider its current position on the crisis.
In his talks with allies, Kerry should seek commitments to alter the current dynamics on the ground in favor of the non-radical, unified opposition. Providing anti-aircraft weapons, training, and intelligence to select opposition fighters would serve this aim, and also provide the United States with much-needed leverage over the often-fractious opposition leadership. Leverage matters now, and will matter equally when the fighting ends and Syria starts trying to rebuild.
Kerry should also make it clear that while Washington backs U.N. envoy Lakhdar Brahimi's peace plan, the United States is determined to see the fighting end soon, not simply facilitate protracted negotiations that buy the Assad regime time.
Russia is well placed to help achieve these goals. Moscow cannot simply order Assad onto a waiting Russian aircraft, but a shift away from reflexive defense of Syria in the U.N. Security Council would be immediately noticed by Assad, and more importantly, by his coterie, increasing the pressure on them to desert. Further isolation of Assad, coming from one of his primary backers, would also be a boon to opposition morale, fueling the sense that momentum is shifting.