Al Qaeda managed to ignite sectarian violence between Sunni and Shiite Arabs with a few well-executed atrocities. This violence seems like an undisputable argument for a weak federation -- or even partition -- but we must beware that any collapse of a strong central authority will likely lead to lengthy "cleansings" within each canton and perhaps even outright warfare between them.

Even the Kurdish region, which presents us with a simpler picture than the rest of Iraq, has a significant Arab population around oil-rich Kirkuk. This suggests that "ethnic cleansing" will intensify there too.

All neighboring countries will be affected as well. The whole region will be shaken.

Turkey, the regional power, fears that a de facto independent Kurdistan with oil wealth will inspire and empower its own separatist Kurds. Ankara will do all in its power to make the Kurdish region in Iraq -- which depends on Turkey for its economic development -- a failure. Also, Turkey has shown its willingness to support military intervention.

Iran will hold sway over a Shiite region in the center and south of Iraq. This will also create new problems for Saudi Arabia, which fears the increasing power of the Shiites in the region and within their own country with Shiites concentrated in oil-rich regions.

In a loose federation, Iraq's Sunnis will find they've lost influence over the country's other groups during the Baath dictatorship. They'll also lose access to Iraq's resources and to the sea. Riven as it already is by extremists in the insurgency, the Sunni region could easily become a failed state and a haven for terrorists. This is something no other country in the region will tolerate and will prompt foreign interference.

Judging by the intensity of the sectarian violence, it seems partitioning Iraq will lead to even greater bloodshed among the country's groups -- and even proxy wars between its neighbors. Countries further afield can only tremble at other failed cases of borders redefined by ethnic and religious groupings.

The problems are evident. The proposals for a solution are neither simple nor comforting. Under Saddam's dictatorship the forces of partition were kept in check by force. Dictatorship is no longer an option.

So now Iraq will only be stabilized if a sufficient military force can provide enough security (and time) for the Kurds and Sunni and Shiite Arabs to agree on a central authority that is strong enough to hold the country together while giving each group its own distinct haven. Otherwise, the bloodletting will continue until, exhausted, each group settles for the best it can get rather than -- as is the case now -- fighting for what it wants. This could lead to failed statelets in the heart of the Middle East. In other words, the U.S. must not withdraw. It must help Iraq reach a federal solution and then give it enough security and time to develop.