Prime Minister Nouri al-Maliki, meanwhile, took a hard line against al-Sadr's Mahdi Army militia and other illegally armed groups, setting conditions for stopping military operations against them that included surrendering weapons.
Al-Sadr's new message, which was read during prayers and posted on his Web site, eased fears that the anti-U.S. cleric was planning to lift a nearly 8-month-old cease-fire, a move that would jeopardize recent security gains.
"If we have threatened an open war until liberation, we meant a war against the occupier," the cleric said in the statement. Al-Sadr is believed to be in Iran.
Mahdi Army fighters have clashed daily with U.S.-backed Iraqi security forces since al-Maliki launched a crackdown against militias on March 25. Last week, al-Sadr issued what he called a "final warning" to the Shiite-led government to halt its offensive or face an "open war until liberation."
But Friday's sermon appeared to be an attempt to ease the showdown. Al-Sadr called on his followers to adhere to the cease-fire order and urged an end to the recent battles, which have left dozens of civilians dead or injured.
"I call upon my brothers in the police, army and Mahdi Army to stop the bloodshed," al-Sadr said in the statement. "We should be one hand in achieving justice, security and in supporting the resistance in all of its forms."
He also appealed to Iraqi troops not to fight alongside the Americans, but did not directly call on his fighters to attack the Americans.
"This is an open war between us and the occupier, so do not interfere in favor of the occupier," he added.
The offensive began in the oil-rich city of Basra, but an Iranian-brokered truce calmed the situation there and the recent fighting has focused mainly in Sadr City, a district of 2.5 million people in northeastern Baghdad.
The Sadrists accuse al-Maliki, a political rival, of trying to sideline them ahead of expected provincial elections in the fall. But they appear divided over whether to launch a full-scale fight against U.S.-led forces or focus on political efforts.
Mahdi Army commanders, who have said they have recently taken delivery of new Iranian weapons, expressed disappointment that the cleric had not given them a green light for an offensive.
"Al-Sadr has made it clear that the open war is directed against the Americans. We will continue to fight the Americans and if the Iraqi soldiers attack us, we will strike back," said one militia commander who identified himself only by his nickname Abu Thar.
Senior al-Sadr aide, Hazim al-Aaraji, however, said the new message was intended to lessen tensions in Basra and Sadr City.
Sadr City residents, who have found themselves under a virtual siege because of the clashes, welcomed the statement.
"It is a sign that al-Sadr is willing to end our misery," said Naji Mohammed, a 42-year-old government employee. "We are without work, services and food."
But al-Maliki, who also has threatened to politically isolate al-Sadr if he doesn't disband the Mahdi Army, laid down four conditions that are unlikely to be met.
In an interview with Al-Arabiya TV, he said the group surrender heavy and medium weapons, cease interference in the affairs of the state as well as the security forces, hand over all wanted people and present lists of names of people involved in violence.
