Iraq's main Sunni Muslim bloc has boycotted a conference aimed at reconciling differences among the country's rival political groups.
A spokesman for the bloc says it was not properly invited. He also says the bloc's political concerns are not being heard.
Iraqi Prime Minister Nouri al-Maliki, a Shi'ite Muslim, opened the conference Tuesday in Baghdad and called on all political leaders to support national reconciliation.
Another group, a Shi'ite party loyal to anti-U.S. cleric Moqtada al-Sadr, walked out of the conference after it began, saying it was merely propaganda and had no substance.
Mr. Maliki is under pressure from the United States to unite Iraq's rival political factions.
In Washington, a State Department spokesman says the U.S. believes in the ability of Iraq's political leaders to collaborate and work out compromises.
In the northern Iraqi city of Irbil, visiting U.S. Vice President Dick Cheney encouraged a top Iraqi Kurdish leader to help pass laws that will foster national reconciliation.
Cheney said the U.S. also is counting on Kurdish leader Massoud Barzani to help build a new strategic relationship between the United States and Iraq.
The vice president held talks Tuesday with Barzani in Irbil in the Kurdish region of northern Iraq.
Barzani said he wanted to assure Cheney that Iraqi Kurds are committed to Iraq's constitution and will continue to play a positive role in building a democratic and free Iraq.
Cheney's visit to Iraq marked his first stop on a Middle East tour. He is now in Oman and also will visit Saudi Arabia, Israel, the West Bank and Turkey.
In violence Tuesday, Iraqi police say four people, including two police officers, were killed in separate bomb blasts in northern Baghdad.
Thirteen other people were wounded in one of the blasts. Police also say a car bomb attack in the northern city of Mosul killed three people and wounded at least 40 others.