U.S. forces continued to scour the caves previously occupied by Al Qaeda forces for clues to the whereabouts of Usama bin Laden on Saturday.

Pentagon officials told Fox News on Friday that the number of U.S. troops on the ground in Afghanistan is likely to rise above 3,000 as troops from the 101st Airborne Division, now in Pakistan, and the 10th Mountain Division, now in Uzbekistan, are added to camps in Mazar-e-Sharif and Bagram where defeated Taliban and Al Qaeda forces are being detained.

Also on Friday, British peacekeepers arrived in the capital of Kabul to help secure the establishment of a new interim government.

The caves "are being triaged and put in priority order," Defense Secretary Donald H. Rumsfeld said. "Then Afghan forces and coalition forces are going into those caves and looking for evidence and people and weapons and trying to determine what we can do to deal with terrorists all across the globe."

U.S. warplanes will be also equipped with a new fuel-air explosive to drop into the cave complexes, a senior Pentagon official said.

Bin Laden is believed to have been holed up in the Tora Bora area before he disappeared, but has thus far eluded U.S. troops and anti-Taliban tribal fighters in the region.

"We don't know if he is alive or dead," said Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff, who joined Rumsfeld at the press conference.

Sending more troops to Tora Bora would raise the risk of casualties, but some military planners believe it is the best way to clarify who among the Al Qaeda network was killed during recent fighting, and, in so doing, gain a better understanding of whether bin Laden is still in that region.

Meanwhile, a convoy of 80 British Royal Marines entered Kabul, the first contingent of multinational peacekeepers launching a six-month mission to protect the new interim government of Prime Minister Hamid Karzai.

The British soldiers were the vanguard of a force that will grow to 3,000 to 5,000 assigned to ensure the safety of the interim cabinet until an Afghan council determines a more permanent government.

"We are very happy that they are coming because this is the only guarantee that we will have peace," said a Kabul baker, Mohammed Sadar.

But many Afghans appeared unwilling to accept a long-term international presence in their capital.

"They should leave Afghanistan when we are sure of peace," said Ghulam Dastigir Khan. "We don't want them to stay forever. We are Muslims. They are not," said Khan, a cigarette vendor who hopes the soldiers will boost his current income of about a dollar a day.

The hunt for Al Qaeda in Tora Bora has been complicated by harsh winter weather and the knowledge that some of the terrorists' abandoned bunkers and caves were probably booby-trapped or mined. It also is possible that some Al Qaeda fighters are laying in wait in some caves, prepared to resume fighting.
  
U.S. officials have said they would like to break into caves whose entrances were sealed shut by U.S. bombing. They believe they will probably find the bodies of Al Qaeda fighters there, as well as potentially useful documents.
  
Of the Al Qaeda materials found thus far in caves, bunkers and in urban buildings throughout Afghanistan, most relate to the group's pursuit of chemical, biological or nuclear weapons, one U.S. official said.
  
The finds have not changed officials' thinking that bin Laden has at most a limited capability to conduct terrorist attacks with crude chemical weapons and that he may have biological or radiological weapons.

Currently, there are about 2,000 Marines in southern Afghanistan, mostly in and around the Kandahar airport, and small pockets of Army troops, including special forces, scattered elsewhere around the country.

Secretary of Defense Donald Rumsfeld and Gen. Tommy Franks, head of U.S. Central Command, are also considering other new moves, including an effort to "re-energize" the Afghan tribal forces who drove Al Qaeda fighters out of the Tora Bora area but are now inclined to consider their part of the war over.

From the U.S. point of view, the war cannot end until bin Laden, Taliban leader Muhammed Omar, and their top deputies are either killed or captured, U.S. officials have said.
 
Rumsfeld is considering whether to provide the Afghan tribal forces with more equipment and weapons in hopes they will continue to pursue Al Qaeda in the Tora Bora area and keep up the hunt for Omar in the Kandahar area, officials said.

The Associated Press contributed to this report.