From the Summary: "Operation Iraqi Freedom overthrew Saddam Hussein's regime, but Iraq remains unstable because of Sunni Arab resentment and a related insurgency, compounded by Sunni-Shiite violence that some believe is now a civil war. Mounting U.S. casualties and financial costs - without clear signs of security progress - have intensified a debate within the United States over whether to wind down U.S. involvement without completely accomplishing initial U.S. goals. U.S. Defense Department reports are expressing more pessimism about security in Iraq and they, as well as Bush Administration officials, are expressing some frustration at the unwillingness of the Iraqi government to disband sectarian militias that are committing violence against civilians of rival sects. U.S. difficulties in Iraq are discussed in the December 6, 2006, report of the Iraq Study Group co-chaired by former Secretary of State James Baker and former House International Relations Committee chair Lee Hamilton, which called the Iraq situation 'grave and deteriorating."
CRS Report for Congress, RL31339