BAGHDAD - The U.S. military should not provoke the Mehdi Army militia of anti-U.S. Shi'ite cleric Moqtada al-Sadr into a return to the widespread violence that took Iraq to the brink of civil war, a report said on Friday.
The International Crisis Group (ICG) think-tank said the Mehdi Army, once described by Washington as the biggest single threat to peace in Iraq, was "unassailable" in strongholds in Baghdad and mainly Shi'ite southern Iraq.
Sadr, the son of a revered Shi'ite cleric killed under Saddam Hussein, led two uprisings against U.S. forces in 2004.
Late on Thursday, U.S. soldiers arrested a senior figure and three others from a "rogue" Mehdi Army unit linked to attacks on U.S. and Iraqi security forces in eastern Iraq's Wasit province. U.S. and Iraqi soldiers also clashed with gunmen in a Sadr stronghold in Baghdad on Thursday.
The ICG report said it was "fanciful" to imagine the defeat of the Mehdi Army, which has tens of thousands of fighters, and that pressuring it would likely trigger fierce resistance in Baghdad and escalate strife among Shi'ites in the south.
Attacks across Iraq have fallen 60 percent since last June, which U.S. officials say is due mainly to an extra 30,000 U.S. troops and the rise of mainly Sunni Arab neighborhood police units.
But the ICG said the drop was mainly due to Sadr's August 29 declaration of a six-month ceasefire. On Thursday he ordered members to maintain the freeze, which expires this month, amid growing signs of impatience in the militia.
The report said militants claiming to be Mehdi Army members had executed "untold numbers" of Sunni Arabs in response to attacks by al Qaeda during sectarian violence in which tens of thousands died and took Iraq to the brink of civil war.
"If the U.S. and others seek to press their advantage and deal the Sadrists a mortal blow, these gains are likely to be squandered, with Iraq experiencing yet another explosion of violence," the ICG report said.
The U.S. military has been aggressively pursuing what it describes as "rogue elements" of the Mehdi Army who it says have defied Sadr's ceasefire order.
The ICG report said the ceasefire gave Sadr the chance to transform his bloc, which it described as a "deeply entrenched, popular mass movement of young, poor and disenfranchised Shi'ites", into a legitimate political movement.
Sadr told six ministers from his movement to quit the government last April when Prime Minister Nuri al-Maliki refused to set a timetable for the withdrawal of U.S. troops from Iraq.
The U.S. military's policy of targeting Sadrist militants and supporting his Shi'ite rivals, the Supreme Islamic Iraqi Council, was understandable but "short-sighted", the ICG said.
The report also said the U.S. military should stop recruiting Shi'ite neighborhood police units to fight the Mehdi Army and concentrate on building a non-partisan security force.
Sadrists often complain of being targeted by U.S. and Iraqi security forces, who in turn say that they will not tolerate criminal activity by "rogue" elements of Sadr's movement.
In Baquba, police declared an indefinite curfew after Mustafa al-Qaisi, a senior leader of neighborhood police units in ethnically and religiously mixed Diyala province, said his groups would not cooperate with U.S. and Iraqi security forces.
Qaisi's declaration came after a long-running power struggle with Ghanim al-Quraishi, the chief of police in Diyala. Several hundred of Qaisi's supporters demonstrated peacefully through Baquba, 65 km (40 miles) north of Baghdad, earlier this week.
Sunni Islamist al Qaeda has regrouped in Diyala and other northern provinces after being squeezed out of former strongholds elsewhere in Iraq.
Additional reporting by Waleed Ibrahim in Baghdad, editing by Mary Gabriel
© 2008 Reuters