Iraq's Sadr Says to Halt Attacks on US Troops

But the Shi'ite cleric, whose Mehdi Army militia fought U.S. forces until 2008, warned that if they did not depart on time, military operations would resume and be "very severe".

"Because of my eagerness to accomplish the independence of Iraq and have the invader forces withdraw from our holy land, it has become imperative for me to stop military operations ... until the invader forces complete their withdrawal," Sadr said in a statement read out by his spokesman, Salah al-Ubaidi.

"If not, the military operation will start again and with new approaches, and it will be very severe."

American troops are scheduled to withdraw fully by Dec. 31, more than eight years after the 2003 invasion, but Iraq's leaders are negotiating with the United States on whether to retain U.S. military trainers beyond 2011.

Sadr warned last month that U.S. military trainers who stayed in Iraq after the end of the year would be targets. About 43,000 remaining troops are due to leave Iraq under a security agreement between the two countries.

While Sadr's Mehdi Army has for the most part been demobilised, U.S. officials say splinter groups have continued to attack U.S. soldiers.

"We shall soon see whether the Promised Day Brigade and others affiliated with al-Sadr's organisation continue to conduct attacks against U.S. forces and the Iraqi government, or if these are just words without the deeds to back them up," U.S. military spokesman Colonel Barry Johnson said in an emailed response to Sadr's statement.

 Although violence in Iraq has dropped dramatically from the height of sectarian fighting in 2006-7, bombings and killings occur daily and Sunni insurgents and Shi'ite militia are still capable of carrying out lethal operations.

Attacks against Iraqi and U.S. security forces have climbed in recent months. While there were no U.S. military casualties in August, 14 U.S. soldiers were killed in June, the deadliest month for U.S. forces since 2008.

Iraqi security forces are seen to be capable of tackling internal threats, but say they still need training for their air and naval defences, and some heavy conventional weaponry.

Ubaidi said if the Iraqi government wanted, Sadrists were ready to secure the roads for U.S. troops as they depart Iraq.

Sadr's political movement is a key ally of Prime Minister Nuri al-Maliki in his fragile coalition mix of Shi'ites, Sunnis and Kurds.

He has in the past threatened to revive the Mehdi Army if U.S. troops stay, but Sadrist sources have said the militia is riven with splinter groups and internal divisions.

U.S. officials and Sunni Arab leaders accused the Mehdi Army of being behind many of the sectarian killings in Iraq after the 2003 U.S.-led invasion that deposed Sunni dictator Saddam Hussein.