AFTER TWO armed rebellions in the past three years, no one can be optimistic about the latest cease-fire in Congo. Rebel forces are so divided that they could not agree who would sign the peace pact; in the end, 50 people from the rebel side all signed. Yet this agreement, a new report from the U.S. Institute of Peace floridly but fairly suggests, represents "a last exit on the region's highway to hell." "It's the best hope, and I think we have to take it seriously and bet on it," says David Smock, a co-author of the report who recently returned from the region.

In a continent too familiar with civil strife, Congo's troubles matter more than most. The former Zaire is a huge nation at the center of Africa, rich in natural resources but mired in poverty and corruption. Its troubles have sucked in many neighboring nations -- Uganda, Zimbabwe, Angola and more. Rwanda and Burundi, sites of terrible ethnic violence in recent years, both are unlikely to find peace if Congo, their giant western neighbor, remains unstable.

Hope for stability was high when Laurent Kabila led a successful rebellion against his nation's longtime, thieving dictator. But Mr. Kabila has disappointed almost everyone; he certainly has not paved the way, as he had promised, toward democracy or reconstruction. Last year a second rebellion broke out, this time with Mr. Kabila's regime as the target, and as in the previous war, civilians have been the foremost victims. A half-dozen neighboring countries lined up on one side or the other.

Now those countries have pledged to withdraw their forces. Internal antagonists have agreed to lay down their arms. There is a promise from all sides to engage in a "national dialogue" on Congo's future. Representatives of civil society, long squelched by Congo's autocrats, are supposed to participate alongside those who have fought in the civil wars.

The obstacles are enormous. But the alternatives to success -- a bloody fracturing of Congo, renewed fratricide in Rwanda and Burundi, deepening disease and poverty -- are frightful. The United States and other wealthy countries should offer as much support as possible to the African leaders who have helped negotiate the pact and to Congo itself. The West should bet on this cease-fire, not because the odds are favorable, but because another failure could be so costly.