An agreement between the United States and Iraq to allow U.S. troops to remain operating in Iraq past 2008 should be put to a popular referendum, Shiite cleric Muqtada al-Sadr urged in an online message to his followers.

In the statement posted on a loyalist Web site, the popular cleric renewed his call for a timetable for the departure of U.S. troops and called for delegations to approach the United Nations, the European Union, the Arab League and other Iraq neighbors to discuss the agreement.

Protests against the agreement should be carried out after Friday prayers “until further notice or until the treaty is canceled,” al-Sadr said.

If the government rejects his call for a referendum on the agreement, al-Sadr will order his offices “to work on collecting millions of signatures opposing” it, the message said.

Some members of Congress have objected to the Bush administration’s plans to handle the agreement without seeking congressional approval.