A conference to reconcile Iraq's warring political groups began to unravel even before it got under way on Tuesday, with the main Sunni Muslim Arab bloc pulling out and protesting it had not been properly invited.
Hundreds of politicians gathered for the conference a day after Vice President Dick Cheney, on a visit marking the fifth anniversary of the March 2003 U.S.-led invasion, hailed what he called "phenomenal" political and security improvements.
The war has cost the United States $500 billion since it began. Tens of thousands of Iraqis have been killed and millions displaced. Almost 4,000 U.S. soldiers have also been killed in the war, a major issue in November's U.S. presidential election.
The boycott by the Sunni Arab Accordance Front, a Shi'ite bloc and smaller groups underlined that while Iraq is no longer on the verge of a sectarian civil war, there are still deep divisions between Shi'ites and Sunnis, Iraq's main Muslim sects.