Sporadic fighting near Najaf and Kufa on Saturday marred a tentative cease-fire between U.S. forces and a militia loyal to rebel cleric Moqtada Sadr, who warned the deal was in jeopardy if U.S. soldiers did not stop patrolling the cities.

Local Najaf political leaders and Sadr advisers traded accusations over who was responsible for the continued fighting in the southern cities. Reports from Najaf said five Iraqis were killed in Saturday's clashes as U.S. troops remained in the streets of Kufa, a stronghold of Sadr support.

[In Anbar province west of Baghdad, three U.S. Marines were killed in combat Saturday, the U.S. military said Sunday. The military also announced the death of a soldier in a mortar attack on May 25 south of Baghdad, in which nine soldiers were injured, and said it was investigating the non-combat death of a soldier based in the northern town of Mosul on Friday, the Reuters news agency reported.]

The fighting in Najaf and Kufa came two days after the U.S. military agreed to stop offensive operations against Sadr's Mahdi Army following two months of heavy fighting. In exchange, Sadr's militia was to withdraw from the cities. In addition, U.S. officials tacitly agreed to delay legal proceedings against Sadr until an Iraqi government takes over. The United States has charged Sadr with the April 2003 murder of a rival Shiite cleric.

The scattered combat was straining the truce, which U.S. officials considered necessary to remove a major threat to Iraq's stability as the June 30 transfer of limited power to an interim Iraqi government approaches.

The chief dispute appeared to concern what force will assume security responsibilities in Kufa and Najaf, which have been controlled largely by Sadr militants since early April. Najaf is home to the shrine of Imam Ali, one of the holiest sites in Shiite Islam, and Sadr preaches each Friday in Kufa.

Sadr has demanded that U.S. forces withdraw from the cities and wants local residents to take over security duties. But U.S. forces, under continuing fire from some Mahdi Army members, rumbled into Kufa on Saturday alongside Iraqi police, after there were signs that insurgents were not leaving as agreed.

"We reject the joint patrols," said Qais Khafaji, Sadr's spokesman in Najaf. "If these patrols come near the shrine, we'll defend it." U.S. forces have tried to proceed with caution during their operations to avoid damaging Muslim shrines.

Adnan Zurfi, Najaf's provincial governor, said U.S. forces were respecting the cease-fire deal and blamed Sadr's forces for failing to comply. He said Iraq's interior minister, Sameer Shaker Sumaidaie, had ordered a contingent of Iraqi police to the region to serve as local security forces.

"The armed men should end their presence in the city so as to show respect for the agreement on their side," Zurfi said at a news conference on Saturday.

The city appeared calmer than it had during weeks of street-to-street fighting between Sadr militants and U.S. forces. But Najaf residents remained skeptical that the cease-fire would actually take hold. "I don't know what truce they are talking about," said Ad Khalid, 33, who owns a car dealership in Najaf. "The Mahdi Army is still in the streets carrying guns, and the U.S. forces are still shooting."

Special correspondent Saad Sarhan in Najaf contributed to this report.

Armed Shiite militiamen patrol a street in Najaf. Outbreaks of fighting between U.S. troops and the militia loyal to rebel cleric Moqtada Sadr are jeopardizing the cease-fire agreement.