BAGHDAD, Iraq (CNN) -- The Mehdi Army cease-fire that has been credited with helping to reduce violence in Iraq since August could end soon, a spokesman for the radical cleric who heads the Shiite militia said Wednesday.
If Muqtada al-Sadr doesn't extend the cease-fire Saturday, it will end Sunday, a spokesman says.
If Muqtada al-Sadr doesn't issue a statement by Saturday extending the cease-fire, the freeze will be over Sunday, said Sheikh Salah al-Obeidi, a spokesman for the cleric.
Speaking from Najaf, the Shiite holy city in southern Iraq, al-Obeidi said the message has been conveyed to Mehdi Army members across the war-ravaged nation.
Although the U.S. military has not had contact with al-Sadr, it is encouraging the cleric to continue the cease-fire, saying it would be "a productive and positive step" in rebuilding Iraq, said Rear Adm. Gregory Smith, a U.S. military spokesman in Baghdad.
News of al-Sadr's impending directive came as Smith expressed concern that Shiite militants from the Iranian-backed Special Groups had staged deadly attacks in Baghdad this week.
On August 28, al-Sadr called for a temporary suspension of Mehdi Army activity, including attacks on police and rival factions. At the time, he said the six-month suspension would allow his militia to be restructured.
The cease-fire followed bloody battles between al-Sadr's militia and fighters from the Badr Organization, the armed wing of the rival Supreme Islamic Council of Iraq, headed by Abdul Aziz al-Hakim. More than 50 people were killed and scores were injured in the skirmishes in Karbala, Baghdad and Babil province.
Days later, the U.S. military applauded al-Sadr's mandate, saying it would allow coalition forces to focus on al Qaeda in Iraq "without distraction from [Mehdi Army] attacks."
In October, al-Sadr and al-Hakim forged a truce in the spirit of the holy month of Ramadan, when gestures of mercy and forgiveness are common, a SICI spokesman said.
Al-Sadr called for calm, banned further fighting and urged his militia members to guard SICI officials and offices in Iraq, an al-Sadr aide said at the time.
Civilian and military deaths began to decline after the August cease-fire. The U.S. military said al-Sadr's mandate -- along with an increase in U.S. troops and the emergence of Concerned Local Citizens security volunteers -- helped curb the violence.
The top U.S. military commander in Iraq has said al-Sadr may have called the cease-fire to avoid alienation in Iraq. The cleric may have reasoned that his militia's activities could have prompted Iraqis to shun the Mehdi Army "in the same way that they rejected al Qaeda in Iraq," said Gen. David Petraeus.
The U.S. military maintained Wednesday that the cease-fire has helped reduce assassinations and Shiite infighting in Baghdad and the southern Shiite heartland.
The "cease-fire has been helpful in reducing violence and has led to improved security in Iraq," Smith said in a news conference. "We would welcome the extension of the cease-fire as a positive step by the [Sadrist movement] to continue its support of rebuilding the new Iraq."
Smith said the Sadrist movement has demonstrated in recent weeks that it "completely supports rebuilding the new Iraq in a peaceful and democratic way and that the extension of a cease-fire would be a productive and positive step in that direction."
Despite the positive trends attributed to the cease-fire, some Shiite militants -- who analysts believe may be more radical than al-Sadr -- have ignored the cease-fire.
Five people were killed and 16 others wounded in an attack Monday at the Baghdad International Airport, the U.S. military said.
Another attack Tuesday in the Rustumiya neighborhood killed a U.S. civilian and wounded several others, Smith said.
The U.S. and Iran, longtime adversaries with no real diplomatic ties, have engaged in talks to address the violence. The talks have been hosted by the Iraqi government.
The U.S. military will await al-Sadr's weekend decision before enacting a contingency plan.
"The cease-fire remains in place and we would hope and expect it would continue," Smith said.
In other developments:
• Iraqi police Wednesday began rounding up homeless and mentally ill people living on the streets of Baghdad to prevent insurgents from using them as suicide bombers, an official with the Iraqi Interior Ministry told CNN. The initial sweep picked up eight beggars: Three women and five men.
• The U.S. military Wednesday said a male detainee died at a coalition medical facility and "the cause of death is under investigation." The facility was not identified but the release comes from the Multi-National Force-West, located in Anbar province. The detainee had been taken to the facility Tuesday "for medical assistance. "
• Three Iraqi children were killed by mortars Tuesday while playing soccer, the U.S. military said Wednesday. Seven children were also wounded in the attack outside a coalition military facility near Balad, the military said.
• A suicide bomber attacked an outdoor market in Diyala province Wednesday, killing at least six people and wounding 18 others, police said. Most of the casualties in the Muqdadiya attack were civilians, according to Col. Ragheb al-Omairi.
• Three U.S. soldiers in a vehicle were killed by a roadside bomb in northwestern Baghdad Tuesday, the U.S. military said Wednesday. The soldiers' deaths bring to 3,966 the number of U.S. service members who have died in the Iraq war.
• A convoy carrying Iraq's deputy industry minister was bombed in the eastern Baghdad neighborhood of Zaiyouna, an Interior Ministry official said. The minister, three security guards and two civilians were injured.
• Iraqi and U.S. troops in Mosul rescued a kidnapping victim, the U.S. military said Wednesday. The victim was found Tuesday handcuffed in "an underground chamber" where he had been confined, Maj. Gary Dangerfield, a military spokesman, said in a news release. A resident tipped off authorities "about a possible terrorist prison and interrogation facility" at a courtyard, Dangerfield said. E-mail to a friend
CNN's Erin McLaughlin, Ahmed Taha and Mohammed Tawfeeq contributed to this report.