The low level civil war, already underway in Iraq, is trending toward major conflict that would be marked by massive ethnic cleansing, pitched battles between Shiite and Sunni militias and intervention by neighboring states. Like most civil wars, this one could last a long time, and it could destabilize the entire Middle East. It would create thousands of refugees, possibly trigger civil wars in neighboring states, and breed new terrorist groups. A full-scale civil war would also interrupt Iraqi oil production, thereby jacking up oil prices to the detriment of major economies around the world.

It was hoped that the Iraq Study Group might divine ways to contain the mess in Iraq, thereby facilitating a gradual American withdrawal. The study group did provide an appropriately dire assessment of conditions on the ground and urged a quick course change by America to avoid a rapid descent into chaos. But after eight months of investigation and deliberation, the high profile, bipartisan study group, co-chaired by James Baker and Lee Hamilton, came up with too little, too late. Many of the 79 recommendations in the Baker-Hamilton report are based on faulty assumptions of cooperation from the hostile parties and a questionable linkage to a barely existent Israeli-Palestinian peace process.

The study group did propose a daunting list of “milestones” to be reached in 2007 by Iraq’s weak central government, thus allowing a 2008 withdrawal of American combat troops. Some 15,000 trainers would be left to transform Iraqi military forces into reliable security providers. The milestones include efforts to placate the Sunnis through power-sharing constitutional changes and an allocation of oil revenues, based on population percentages.

To date, the Shiite- and Kurdish-dominated government has been unwilling to compromise on these key issues. The prospect of attitudinal change appears slim, given the angry rejection by Shiite and Kurdish leaders of the study group’s recommendations. Even if they were to relent, there is little chance that the Sunnis would trust paper agreements beyond the time American troops were on hand to enforce compliance. As for Iraq’s army, the thought that it can become an effective and trusted keeper of the peace between the warring sects is a case of hope trumping experience. In short, the brutal and rising sectarian violence has magnified hatred and sown distrust among all the parties.

The potential of the Iraq Study Group was further undermined by its reception elsewhere. In America, conservative Republicans condemned the report as a ticket for defeat, with lasting harm to American interests around the world. Many congressional Democrats were lukewarm to what they considered a vague and drawn-out plan for withdrawal. For his part, President Bush demurred on engagement with Iran and Syria and pointedly looked forward to forthcoming recommendations from the Pentagon, the administration’s own security officials, and selected think tanks. In Israel, the government and press roundly criticized the Baker-Hamilton report for opening the door to bargaining with Syria and Iran.

America will have to consider other options than those from the study group, if civil war becomes unavoidable between irreconcilable Iraqis. Most civil wars end, not by mediation, but by one party’s overwhelming victory. Thus, some students of civil wars advise staying out of the middle while the hostile parties fight to an exhausted end. This option is irresponsible given the high chance of igniting regional conflict in the Middle East. A variation calls for getting out of the middle but staying engaged by supporting the likely winner. This variation also pales when taking into account the particular characteristics of the Middle East. Backing either the Sunnis or the Shiites in Iraq would enrage their fellow believers and governments in neighboring states.

As the Iraq Study Group made plain, there are no good options for “victory” as defined by the Bush administration. Democratization of the region has been set back by the intervention in Iraq and will take years of patient work by players within the Middle East. And solutions to the Israeli-Palestinian conflict are not at hand. The best that can be expected of outside mediation is some containment of the violence. Neither democratization nor conflict resolution can move forward without first achieving some reasonable measure of stability.

To that end, some of the study group’s recommendations could be helpful, especially those emphasizing better diplomacy, evenhanded mediation, and engagement of the international community. As for military forces, America needs a continuing presence. However, large bases and troops on the ground may needlessly inflame the Arab Muslim populace. Some analysts think that potent American air and naval forces provide sufficient offshore capabilities to meet any security challenges.

Given the need for Middle East oil and gas, America must continue the search for regional stability through the right mix of engagement, incentives, and deterrents. America cannot simply vacate the premises. Any vacuum is likely to be filled with disruptive violence. That should be the lesson learned from the six-year absence of America from the search for peace between Israelis and Palestinians.

Mr. Hoge is editor of Foreign Affairs.