Updated

Afghan tribal chiefs on Wednesday gave Usama bin Laden's Al Qaeda fighters a new ultimatum to lay down their arms by midday Thursday (2:30 a.m. EST) and turn over their leaders.

American AC-130 gunships continued bombing during the negotiations, attacking a desolate canyon in the White Mountains where a group of Arabs and other non-Afghans fighting for Al Qaeda were trapped.

Ghafar, a leader in the tribal eastern alliance, said the Al Qaeda fighters are believed to include some from a list of 22 "most wanted terrorists" made public by the Bush administration after the Sept. 11 terror attacks in the United States.

"They have to hand them over, but they didn't (want to)," said Ghafar, who goes by one name. He said a plan for the fighters to surrender Wednesday morning collapsed in part over the refusal of leaders to give up. "They must turn over at least some of these people."

He said it was not certain if bin Laden, the suspected mastermind of the Sept. 11 terrorist attacks, was among them. U.S. and Afghan officials have said he may be in the Tora Bora region of caves and tunnels, where the eastern alliance — backed by U.S. bombing — has been attacking Al Qaeda.

Gen. Peter Pace, the vice chairman of the joint chiefs of staff, said in Washington that the Pentagon does not know if the Al Qaeda leadership was in the Tora Bora area. He said it would be "great" if they were.

An undetermined number of foreign fighters is in the heavily forested canyon, where they fled after being routed from their mountaintop positions and caves the day before. The alliance had given them until 8 a.m. Wednesday to give themselves up, but the deadline passed with no surrender.

Ghafar said that during negotiations it became clear that only low-level Al Qaeda fighters planned to turn in their weapons and that senior officers would not.

The alliance suspected that top Al Qaeda leaders would have used any surrender to flee in small groups to other areas of Afghanistan or across the nearby border to Pakistan, he said. Thousands of Pakistani troops have deployed on the frontier to cut off escape routes.

U.S. warplanes kept up their assault at Tora Bora. AC-130s struck for a second straight night Wednesday, and during the day B-52s pounded the Al Qaeda positions in a roughly 10-square-mile area.

During fighting Wednesday, about 60 U.S. special forces soldiers were on the front line, wearing traditional Afghan hats and shawls, but carrying U.S. weapons and large backpacks, making them stand out from the alliance fighters.

Pace confirmed that U.S. troops were in the area but said he was "not aware" of any contact between them and Al Qaeda.

Ghafar said the surrender negotiations were "just a beginning" and might not bring a stop to the battle at Tora Bora. He said his men had pulled back from mountain positions they took in fighting Tuesday because of intense cold, and some Al Qaeda followers may have taken advantage of that to move back in. Other Al Qaeda fighters could still be lurking in the area.

"No one knows how many fighters are up there, but I don't think there are very many. This area is very large. The forest is very dense, and it is very difficult to search," he said.

By late afternoon, heavy machine-gun fire echoed down the Milawa valley, where the Al Qaeda fighters were believed to be hiding in cedar and pine forests that were described as so dense that sunlight couldn't reach the ground. Huge plumes of smoke and dust rose from behind the mountains.

At sunset, an emissary sent by alliance defense chief Mohammed Zaman met with an Arab religious leader to discuss another attempt to organize a surrender for Thursday morning, a senior Zaman aide said on condition he not be named. Ghafar said Al Qaeda had until midmorning to comply, or face an assault.

But there was discontent within the eastern alliance over Zaman's negotiations.

"The fighting will continue, I don't know anything about surrender talks," said militia leader Haji Zahir, son of Nangarhar provincial governor Abdul Qadir. One of his aides said his men were preparing to attack Thursday.

"We don't accept this talking," the aide, Atiaulluh Racham, said. "They (Al Qaeda) want the time to save themselves from this drama."

In other developments:

— An Air Force B-1B bomber flying a long-range combat mission to Afghanistan crashed in the Indian Ocean on Wednesday, and all four crew members were rescued, Pentagon officials said.

— FBI agents questioned John Walker, an American who joined Taliban fighters, at a Marine base in southern Afghanistan. Walker said in earlier questioning that a new Al Qaeda terror attack was possible by the end of the Islamic holy month Ramadan, but the White House cast doubt on the report, saying the 20-year-old would not have knowledge of such plans.

— U.N. Secretary-General Kofi Annan called for the quick deployment of a multinational peacekeeping force in Afghanistan and said he hoped Britain would agree to lead it.

— New Afghan leader Hamid Karzai arrived at the presidential palace in Kabul, the capital, on Wednesday, officials said. Karzai, named interim leader at a U.N.-brokered conference last month, had not been in Kabul since his appointment.

The Associated Press contributed to this report.