Shiite Muslim cleric Moqtada Sadr signaled that he would accept a plea from Iraqi political leaders to dissolve his militia and vacate the sacred Imam Ali shrine in Najaf, but he asked for further negotiations with Iraq's interim government to work out details, according to a letter from Sadr's office that was delivered Wednesday to a political conference here.

Sadr's offer did not specify any conditions, but it also did not indicate when he planned the pullout from the shrine and the dissolution of his militia. His correspondence, a response to a communique issued this week by delegates at the political conference, arrived in Baghdad shortly after Iraq's defense minister warned of a "decisive battle" if Sadr's fighters did not surrender within hours.

Although fighting in Najaf did not escalate after the warning, it did not subside either, as U.S. forces continued to battle Sadr's militiamen in neighborhoods around the shrine.

U.S. and Iraqi officials expressed skepticism about whether Sadr would follow through, particularly with the pledge to disband his militia. Sadr has agreed several times in the past to peace deals with Iraqi officials, only to renege on them later.

"We're taking this with a big grain of salt," said a U.S. official familiar with the Sadr confrontation. "He's made a lot of promises before and he's broken all of them."

Sadr's offer came in a letter delivered by Jalil Shamari, a delegate to the political conference and a member of the Dawa party, a prominent Shiite organization that is not affiliated with Sadr. Shamari, who told reporters that he had received the letter from Sadr's representatives in Baghdad earlier in the day, said the offer was "an entrance to negotiation."

"A delegation from the government will go to Najaf or a delegation will come from Najaf to the government to start the negotiations, which we hope will end the crisis," he said.

Iraq's Defense Ministry responded to Sadr's letter by ordering members of his militia, the Mahdi Army, to lay down their weapons and leave the shrine immediately. The ministry said militiamen would be granted amnesty only if they ended their rebellion in Najaf, about 90 miles south of Baghdad, and other cities.

At the political conference, Sadr's offer was greeted warmly by the more than 1,000 delegates, whose efforts to resolve the crisis in Najaf dominated a meeting convened to select an interim national assembly.

On Monday, the conference issued a communique demanding that the cleric join the political process, disarm and dissolve his Mahdi Army, and vacate the shrine in Najaf. An eight-member delegation from the conference went to Najaf on Tuesday to deliver the demands but failed to meet with Sadr as fighting continued around the shrine.

On Wednesday, to rousing applause from delegates, Shamari said: "Today Moqtada Sadr accepted the three items that are in the letter coming from your national conference with the desire to stop bloodshed in Iraq and to build a new Iraq, which needs the effort of everyone."

"We ask of the conference to make peace, because real courage is to choose the path of peace and use it to build our beloved country," Shamari said. "I'd like to ask this conference for a mechanism to follow up this issue."

One of Sadr's spokesmen, Ahmed Shaibani, warned that withdrawal from the shrine would require "some preparation."

Even if Sadr disbands his militia, keeping its adherents disarmed is likely to be a long and complicated process. U.S. officials say many, if not most, members of the Mahdi Army are young men who joined up not out of religious fervor but because the militia offered them a job and a chance to vent their anger at the U.S. occupation. International experts on militias, including U.N. officials, have suggested that financial incentives might be needed to encourage compliance.

The news of Sadr's letter broke at the conference hours after Defense Minister Hazim Shalan said that the cleric had only hours to vacate the shrine in Najaf. "They have a chance," Shalan told reporters after meeting local officials in the holy city.

"In the next few hours they have to surrender themselves and their weapons. We are in the process of completing all our military preparations," he said. "We will teach them a lesson they will never forget."

Sadr's aides condemned the threat. "The statements of the so-called defense minister are not suited with what the delegation came with," Abdul Hadi Darraji, Sadr's spokesman in Baghdad, told al-Arabiya television. "There is a clear accord from the side of Sayyid Sadr. I think that the statements of the defense minister are personal statements." Sayyid is a title of respect.

Shalan had spent Tuesday closeted with senior military commanders just outside Najaf, poring over plans for military operations in the city. The plans were to be presented Thursday to the top commander of U.S. forces in Iraq, Lt. Gen. Thomas F. Metz.

Overnight, one Marine was killed and another was wounded by mortar shells fired from beside the shrine into the nearby Valley of Peace cemetery, where U.S. forces continued to engage militiamen in sporadic clashes.

U.S. commanders responded by firing a 155mm howitzer toward the shells' point of origin -- closer to the mosque complex than had been previously authorized for artillery fire.

"That was a first," said Maj. Bob Pizzitola, executive officer of the 1st Battalion, 5th Regiment of the Army's 1st Cavalry Division, which is fighting in the cemetery with Marine support.

"It was closer than I thought they'd allow, but it was safe," said Maj. David Holahan of the 11th Marine Expeditionary Unit, which has been commanding the fight in Najaf.

Meanwhile, M1-A1 Abrams tanks and Bradley Fighting Vehicles continued to roam Najaf's old city, a district of houses and shops along narrow streets south and east of the shrine. Combat was sometimes heavy, witnesses said, as the 1st Cavalry's 7th Regiment sought to assert its presence in the quarter.

Twenty-four people were reported wounded or dead before noon, including six women and four children, said Falah Muhanna, the head of Najaf's Health Directorate.

Iraq's interim government has emphasized that any military move to push Sadr's forces out of the shrine would be led by Iraqi forces. But U.S. armor, helicopters and warplanes in recent days have ventured close to the sacred site.

"As for entering the shrine, it will be 100 percent Iraqis," Shalan said. "Our sons of the National Guards are well-trained for the breaking-in operation and it will be easy within hours."

Elsewhere in Iraq, the U.S. military announced it was deploying reinforcements to put down a rebellion near the city of Kut, southeast of Baghdad. In earlier fighting there, four civilians were killed and four injured when they were caught in crossfire between the U.S. forces and insurgents, according to a military statement.

Vick reported from Najaf.

U.S. soldiers fire an antitank rocket at an insurgent position near the Valley of Peace cemetery in Najaf, 90 miles south of Baghdad. A doctor tends to an Iraqi who was wounded by a mortar shell that landed outside his family's home in Najaf, where U.S. forces battled militiamen around the Imam Ali shrine.