What’s the biggest threat to world peace right now? Despite the horror, it’s not chemical weapons in Syria. It’s not even, for the moment, an Iranian nuclear weapon. Instead, it’s the possibility of a wave of sectarian strife building across the Middle East.

The Syrian civil conflict is both a proxy war and a combustion point for spreading waves of violence. This didn’t start out as a religious war. But both Sunni and Shiite power players are seizing on religious symbols and sowing sectarian passions that are rippling across the region. The Saudi and Iranian powers hover in the background fueling each side.

As the death toll in Syria rises to Rwanda-like proportions, images of mass killings draw holy warriors from countries near and far. The radical groups are the most effective fighters and control the tempo of events. The Syrian opposition groups are themselves split violently along sectarian lines so that the country seems to face a choice between anarchy and atrocity.

Meanwhile, the strife appears to be spreading. Sunni-Shiite violence in Iraq is spiking upward. Reports in The Times and elsewhere have said that many Iraqis fear their country is sliding back to the worst of the chaos experienced in the last decade. Even Turkey, Pakistan, Bahrain and Kuwait could be infected. “It could become a regional religious war similar to that witnessed in Iraq 2006-2008, but far wider and without the moderating influence of American forces,” wrote Gary Grappo, a retired senior Foreign Service officer with long experience in the region.

“It has become clear over the last year that the upheavals in the Islamic and Arab world have become a clash within a civilization rather than a clash between civilizations,” Anthony Cordesman of the Center for Strategic and International Studies wrote recently. “The Sunni versus Alawite civil war in Syria is increasingly interacting with the Sunni versus Shiite tensions in the Gulf that are edging Iraq back toward civil war. They also interact with the Sunni-Shiite, Maronite and other confessional struggles in Lebanon.”Some experts even say that we are seeing the emergence of a single big conflict that could be part of a generation-long devolution, which could end up toppling regimes and redrawing the national borders that were established after World War I. The forces ripping people into polarized groups seem stronger than the forces bringing them together.

It is pretty clear that the recent American strategy of light-footprint withdrawal and nation-building at home has not helped matters. The United States could have left more troops in Iraq and tamped down violence there. We could have intervened in Syria back when there was still something to be done and some reasonable opposition to mold.

At this late hour, one question is whether the sectarian fire has grown so hot that it is beyond taming. The second question is whether the United States has any strategy to limit the conflagration.

Right now, President Obama is focused on the imminent strike against the Assad regime, to establish American credibility when it sets red lines and reinforce the norm that poison gas is not acceptable.

But the president does have the makings of a broader antisectarian strategy. He has at least three approaches on the table. The first is containment: trying to keep each nation’s civil strife contained within its own borders. The second is reconciliation: looking for diplomatic opportunities to bring the Sunni axis, led by the Saudis, toward some rapprochement with the Shiite axis, led by Iran. So far, there have been few diplomatic opportunities to do this.

Finally, there is neutrality: the nations in the Sunni axis are continually asking the United States to simply throw in with them, to use the C.I.A. and other American capacities to help the Sunnis beat back their rivals. The administration has decided that taking sides so completely is not an effective long-term option.

Going forward, there probably has to be a global education effort to reduce anti-Sunni and anti-Shiite passions. Iran could be asked to pay a higher price not only for its nuclear program, but for its mischief-making around the region.

But, at this point, it’s not clear whether American and other outside interference would help squash hatreds or inflame them. The legendary diplomat Ryan Crocker argues in a recent essay in YaleGlobal that major outside interventions might only make things worse. “The hard truth is that the fires in Syria will blaze for some time to come. Like a major forest fire, the most we can do is hope to contain it.”Poison gas in Syria is horrendous, but the real inferno is regional. When you look at all the policy options for dealing with the Syria situation, they are all terrible or too late. The job now is to try to wall off the situation to prevent something just as bad but much more sprawling.