Despite Nouri al-Maliki's plea for peace, violence killed at least 20 Iraqis and wounded 37 a day before the official start of the Muslim holy month. Two U.S. Marines died in combat in restive Anbar province west of Baghdad, the U.S. military said.

Shiite, Sunni Arab and Kurdish political leaders broke a two-week deadlock and agreed on a compromise that will allow parliament to take up Shiite-proposed draft legislation to permit creation of partly self-ruling regions.

Sunni Arabs have fought the federalism bill, fearing it will splinter the country and deny them a share of Iraq's oil, which is found in the predominantly Kurdish north and the heavily Shiite south.

But they agreed to a legislative debate after all parties accepted a Sunni demand that a parliamentary committee be set up to study amending the constitution. The committee will be named Monday and the federalism bill will be read to 275-member parliament a day later.

Sunni Arabs hope to win an amendment that would make it more difficult to establish autonomous regions.

The deal opened the way for Iraq's communities to move ahead politically and solve an impasse that threatened to further sour relations between them. If left unresolved, the deadlock could have further shaken Iraq's fragile democracy and led to more sectarian violence.

The parliamentary committee will be made up of 27 legislators from all ethnic, sectarian and religious coalitions and parties. It will have four months to propose amendments, which then would have to be approved by a majority in parliament before being put to a national referendum.

"I expect the work of the committee will last for about one year," Dhafir al-Anihe, a lawmaker with the Sunni Arab National Accordance Front, told The Associated Press.

The federalism bill will be read to the legislature Tuesday and then debated for two days before parliament breaks for the Iraqi weekend. The legislation would be read again, with any changes made by legislators, next Sunday.

A vote would come four days after the second reading, with the bill needing a simple majority for passage. If approved, it would be implemented 18 months later, according to the deal made by the parties, allowing time for consideration of constitutional amendments.

"That was our agreement," Accordance Front legislator Hassan al-Shammari said.

The legislation calls for setting up a framework that would allow creation of autonomous regions in the Shiite south, much like the self-ruling Kurdish region in northern Iraq.

Sunni Arabs warn that setting up such regions could intensify sectarian divisions that have brought months of retaliatory killings between Sunnis and Shiites.

Although federalism is enshrined in the constitution approved by Iraqis in a referendum a year ago, the right to seek amendments to the charter was a key demand made by Sunni Arabs when they agreed to join al-Maliki's national unity government in the spring.

The depth of enmity between Shiites and Sunni Arabs was evident in their disagreement over the day Ramadan was to begin.

Sunni Arabs began observing the month of daytime fasting Saturday, while Iraq's most influential Shiite cleric, Grand Ayatollah Ali al-Sistani, declared the start to be Monday. The Shiite-led government followed al-Sistani's lead.

Sectarian violence has been intense in Baghdad this year. A Saturday bombing in the Shiite slum of Sadr City killed at least 38 people buying fuel for Ramadan. A Sunni Arab extremist group claimed responsibility, saying it was revenge for an attack by gunmen Friday on Sunni Arab homes and mosques that killed four people.

A lawmaker loyal to radical Shiite cleric Muqtada al-Sadr, whose stronghold is in Sadr City, demanded that Sunni Arabs take action against the group behind the bombing.

"All our brothers in religion should declare their innocence from such acts in order to isolate those criminals," Falah Hassan Shanshal said in a statement to parliament.

Earlier, the prime minister pleaded for peace and unity.

"We are all invited to make use of these days to strengthen the bonds of brotherhood and avoid anything that could hurt the social fabric of the Iraqi people," al-Maliki said in s statement.

"Iraq is living in a very sensitive and historic period, either we live as loving brothers side by side and undivided by sectarianism or Iraq will shift into an area for settling accounts of political parties."

At least 20 people were killed and 37 injured Sunday in scattered violence around Iraq, including a mortar attack on the Health Ministry in Baghdad and a car bombing aimed at a police patrol in the city. Police also discovered 13 more apparent victims of sectarian death squads.

The prime minister's office said Iraqi forces had arrested a leader and seven aides in the 1920 Revolution Brigades, also known as the al-Ashreen Brigades, a group responsible for attacks and kidnappings. It said they were caught Saturday northeast of Baghdad, but gave no further details.