One of the biggest obstacles to solving the problem in Iraq is the fact that the country is being fought over by two warring tribes that have been at each others' throats for as long as anyone can remember.
These groups have quite different visions of the future, and they seem determined to resist any sort of compromise. The majority faction continues to exert its control by whatever means necessary; the minority knows that the occupying force will be forced to leave in 2008 and plans to keep the pot stirred until then.
The Shiites and the Sunnis? No, I'm talking about the Republicans and Democrats.