"Thank you, my dear friends, and God bless you,"Shiite radical leader Moqtada al- Sadr replied to an offer from his loyalists of the disbanded Mahdi Army militia to carry out suicidal operations against US Troops there, a statement from Sadr's office in the central shrine city of Najaf said.
The message came from "a group from the Mahdi Army who say they are ready to place themselves under his command to carry out suicide attacks to defend Islam and Iraq, targeting the occupying infidels without hitting civilians or public institutions," Sadr's office said.
In April, Sadr threatened to reactivate the Mahdi Army, which he formally disbanded in 2008, if US forces do not withdraw at the end of the year as scheduled under the terms of a bilateral security pact.
Nearly 50,000 American troops are still in Iraq, down from a peak of more than 170,000 after the invasion of 2003.
US officials have repeatedly asked Baghdad if it wants some troops to stay beyond 2011, but threats and pressure from Sadr have made calling for an extension a difficult decision for Iraqi leaders.
The once powerful Mahdi Army, which fought repeatedly against Iraqi and US-led coalition forces between 2004 and 2007, has been identified by the Pentagon as the main threat to stability in Iraq.
Before it was disbanded, the militia numbered some 60,000 fighters with fierce loyalty to Sadr.
The anti-US cleric, who has been pursuing off-and-on religious studies in the Iranian clerical centre of Qom, is the son of revered Grand Ayatollah Mohammed Sadiq al-Sadr, who was assassinated by regime of now executed dictator Saddam Hussein in 1999.