The ongoing confrontation in the holy city of Najaf appeared to be reaching some sort of climax Friday as a spokesman for Shiite cleric Moqtada Sadr said the keys to the embattled shrine of Imam Ali had been turned over to representatives of Iraq's most influential cleric, Grand Ayatollah Ali Sistani.

Sadr's spokesman, speaking by phone from inside the gold-domed shrine, said it would be cleared of militiamen.

It was uncertain whether that had actually occurred, however. There were still some gunbattles between U.S. troops and Sadr militiamen at mid-day. And conflicting reports flowed throughout the afternoon, including a widely reported claim by a government official early in the day that Iraqi police were in control of the shrine. The police later denied that.

Later in the evening, Adnan Zurufi, the governor of Najaf province, said, "There are still some militia in there." He said the police want to enter the mosque but are awaiting "orders from Baghdad." He also said police had arrested about 50 militiamen at checkpoints around city.

In addition, an aide to Sistani said Friday evening that the grand ayatollah's representatives had not taken control of the shrine because they were waiting for the militia to leave. Speaking to the Associated Press from London, where Sistani is undergoing medical treatment, Sheik Hamed Khafaf said, "If they want to vacate the holy shrine compound and close the doors, then the office of the religious authority in holy Najaf will take these keys. Until now, this hasn't happened."

It did appear in Najaf that Iraqi police were anticipating an exodus from the mosque as they were preparing to establish checkpoints around the city to apprehend militiamen.

A general flight of militiamen from the mosque could make them more vulnerable to U.S. attack. On the other hand, they could disperse into the narrow and crowded streets and pathways of Najaf and regroup later.

No one seemed certain, meanwhile, as to the whereabouts of Sadr.

"The situation is not terribly clear now," Iraq's national security adviser, Mowaffak Rubaie, said on CNN as evening approached in Baghdad.

It was the latest chapter in a tense, arm's-length exchange aimed at avoiding a violent showdown at the shrine, one of the holiest sites for Muslims around the globe.

An unknown number of Sadr's militiamen, known as the Mahdi Army, have been holed up in the shrine for days, using it as a refuge from U.S. and Iraqi forces who have set up a tight cordon around the area.

Iraq's interim prime minister, Ayad Allawi, and a delegation of Iraqi political leaders have been attempting to negotiate an end to the standoff all week. As recently as Thursday night, Allawi had expressed frustration at Sadr's failure to come to terms and issued a "final call" for the cleric to dissolve his militia and abandon the mosque.

Sadr's office issued an unsigned letter on Thursday night that aides said was written by the cleric and bore his seal. The letter called on his followers "to hand over the keys of the shrine to [Shiite religious leaders] as fast as possible so we will prevent infidels from entering this holy place."

But the letter rejected the other central demand of the Iraqi government, the dissolution of Sadr's militia, saying it is a volunteer organization that belongs to Imam Mahdi, the Shiite messiah.

"Let everyone know that this army is the Imam Mahdi's base and I have no right to ever disband it," the letter said.

On Friday, Ahmed Shaibani, the Sadr spokesman, said the transfer to representatives of Sistani had now occurred. But there was no indication that Sadr had accepted Allawi's other conditions.

Allawi, meanwhile, told the BBC that "we are not going to attack the mosque, we are not going to attack Moqtada Sadr and the mosque, evidently we are not going to do this."

The latest flurry of promises and announcements came after the most intense night of U.S. military activity since the current conflict began Aug. 5. Thumping fire from two AC-130 Spectre gunships lit up the night sky and shook homes in Najaf's battered downtown for several hours.

Iraq's health ministry announced 77 dead and 70 wounded in the previous 24 hours, which included a devastating mortar attack by militia on Najaf's police headquarters.

The overnight pounding by U.S. artillery and aircraft fired speculation that a military push for the shrine was underway by U.S. and Iraqi forces. But commanders explained that most of the fire was, in fact, defensive.

A small convoy had gotten stuck in the muck of a supposedly dry lake bed to the west of the shrine. While the vehicles were immobilized, militiamen rained mortars and gunfire down on the exposed troops.

"It worked out to our advantage," said Lt. Col. Myles Miyamasu, who commands the 1st Battalion of the 1st Cavalry's Division 5th Regiment. "We had clear fields of fire and killed maybe 17 of them: three snipers, five machine gunners and two or three mortar crews. You just couldn't ask to be stuck in a better place."

Friday was quiet for much of the day, in part because U.S. forces halted offensive operations for several hours at midday to show respect for noon prayers, according to commanders.

The halt was lifted in early afternoon, however, and as the flurry of new developments surfaced field officers said their orders to keep the Mahdi Army off balance remained unchanged.

Chandrasekaran reported from Baghdad; Barbash reported from Washington.