The militia of Shiite cleric Muqtada al-Sadr has declared a unilateral cease-fire with U.S. forces in the Baghdad district of Sadr City and has offered to help police ensure safety in the area, a statement said Friday.

The cease-fire went into effect Thursday and was "obligatory on all al-Mahdi army's heroes," according to the statement, issued by the central committee of al-Sadr's al-Mahdi Army (search) and distributed in the Shiite district.

The declaration said the cease-fire was called to show al-Sadr's interest in preventing "terrorists and saboteurs" from "causing overwhelming chaos or security disorder."

The militia offered "to actively contribute and positively cooperate with the honest parties in Iraqi police and the national forces" in order to secure the "safety of institutions, Iraqi state buildings and government buildings" as well as water, power, fuel and refineries.

Clashes had been occurring regularly between U.S. soldiers and al-Sadr's fighters in parts of Baghdad despite the truce that ended the armed standoff several weeks ago in the Shiite holy cities of Najaf (search) and Kufa (search).

In early April, al-Sadr launched an uprising throughout the Shiite heartland south of the capital after the coalition closed his newspaper, arrested a top aide, and announced an arrest warrant charging him in the April 2003 murder of a rival cleric in Najaf.

Al-Sadr's position was weakened, however, due to heavy casualties suffered by his fighters in Karbala and Najaf and to pressure from the mainstream Shiite hierarchy eager for an end to the armed standoff with the Americans.

Al-Sadr accepted a deal to end the clashes around Shiite shrines in Najaf and Kufa and turn security over to the Iraqi police in return for a dialogue on his future with the Shiite leadership.

The United States, which has vowed to "capture or kill" al-Sadr, has tacitly agreed to let the new Iraqi government deal with him.