Najaf, Iraq ? With American troops closing in and a growing number of his gunmen in hiding, radical Shiite Muslim cleric Muqtada al-Sadr on Wednesday offered unconditional talks with U.S. authorities seeking to kill or capture him.

His spokesman in Najaf said al-Sadr, whose men have launched widespread attacks on American forces in the last week, was retreating further by dropping demands that U.S.-led coalition forces withdraw from residential areas, free Iraqi detainees and end the siege of Fallujah before negotiations could proceed.

Al-Sadr’s apparent effort to reduce tensions is a concession to Iraq’s high-ranking ayatollahs — the most senior Shiite religious leaders — who are trying to avoid bloodshed in this holy city and who oppose any U.S. action to arrest a Shiite cleric. But the spokesman, Sheik Qais al Khazali, said the cleric wouldn’t disband the Mahdi Army militia as the United States demanded and that any attempt by coalition forces to enter Najaf would be met with armed resistance.

There’s no indication yet that American authorities are willing to negotiate with al-Sadr. Lt. Gen. Ricardo Sanchez, the commander of American forces in Iraq, said Monday that “the mission of the U.S. forces is to kill or capture Muqtada al-Sadr.”

Al-Sadr is an upstart young cleric whom many more established religious figures reject, but he’s successfully drawn support from them in his confrontation with U.S. forces.

Al-Sadr’s supporters — including Sunni Muslim sympathizers, who usually oppose Shiites and their clerics — have been attacking coalition forces across central and southern Iraq. They’ve also taken control of several city centers.

“We’ve accomplished a lot thus far, including uniting the Shiites and Sunnis to fight the Americans,” Khazali said. “We also paved the way for Iraqis to set aside their (ethnic and religious) differences. For those reasons, it’s been worth spilling so much blood.”

U.S. forces are seeking to arrest al-Sadr in connection with the slaying of a pro-Western Shiite cleric a year ago in a violent confrontation that drove Iraq’s Shiite spiritual leaders into seclusion and brought al-Sadr to the attention of Iraqis and Americans. They also want to destroy al-Sadr’s Mahdi Army, which is made up of thousands of largely poor and uneducated Iraqis.

A 2,500-strong U.S. force, backed by tanks and artillery, was massed Wednesday on the outskirts of Najaf and neighboring Kufa, where al- Sadr delivers his fiery sermons. Troop movements in the area raised fears of an American assault and sent more Mahdi troops into hiding with their Kalashnikovs, rocket-propelled grenades and other weapons.