U.S. military officials still don't know where Usama bin Laden may be hiding — or if he's still alive — but the war commander leading the effort warned Friday that "the world is not large enough a place for him to hide."

"We're in the speculative sort of world," Army Gen. Tommy Franks told reporters. "Bin Laden could be alive, dead, or in Afghanistan or not."

Franks, however, dismissed speculation by Pakistani President Pervez Musharraf that the terrorist leader may have died of kidney failure. He said none of his intelligence reports confirmed or denied that.

"Right now, I honestly don't know where he is," said Franks, head of U.S. Central Command, based in Tampa, Fla. "The world is not a large enough place for him today. He may hide today, he may hide tomorrow but the world is not large enough a place for him to hide."

Franks said the U.S. military has been going through Taliban and Al Qaeda safehouses, caves and other sites where they have found documents and other materials that could prevent future attacks.

"That is, of course, the very first thing we're looking for — to be able to pre-empt activity that may have already been planned," he said.

Information gleaned from Afghanistan helped authorities in Singapore disrupt a planned terrorist action against U.S. facilities in that country.

Franks said officials have obtained "a great many pieces of documentary evidence, diaries, hard drives, whole computers."

Prisoner interrogations have become a main focus of U.S. military and intelligence operations in the search for bin Laden. One hundred and ten prisoners have been taken to Guantanamo Bay, Cuba, including Mullah Fazel Mazloom, the Taliban army chief of staff who is the highest-ranking member of the deposed Afghan government now in U.S. custody, according to defense officials.

Mazloom surrendered to anti-Taliban Afghan forces in the battle for the city of Kunduz in November, survived a bloody prisoner uprising later in Mazar-e-Sharif and then was turned over to the United States.

More than 300 other Al Qaeda and Taliban prisoners are in U.S. custody in Afghanistan. Some are being returned to Pakistan.

Al Qaeda training camp commanders Ibn al-Shaykh al-Libi and Abd al-Hadi al-Iraqi are also in U.S. custody.

Yemeni officials said al-Libi warned of an impending attack on the U.S. Embassy in Yemen. They did not say when the attack was to take place. The U.S. Embassy in San`a suspended most consular services on Monday.

The prisoners may provide some new direction for the military and CIA reconnaissance effort in the region.

Pentagon officials said surveillance aircraft flying over Afghanistan and U.S. troops on the ground are watching numerous areas of the country in hopes of finding bin Laden and the other Al Qaeda and Taliban leaders. Navy ships and patrol planes are monitoring the waters off Pakistan's coast in case anyone tries to slip away by sea.

"This is like any other manhunt," said Loren Thompson, a military analyst at the Lexington Institute. "The more time that goes by, the farther away the suspect may be."

Human intelligence on bin Laden's whereabouts, perhaps provided by someone seeking the $25 million reward, may be the most likely avenue to finding him, experts said.

"You're waiting for a break," said Ivo Daalder, an analyst at the Brookings Institution. "He could well be going underground for more than a year. This is a war to the finish for him."

The improved intelligence-sharing network between the United States and places such as Yemen and Sudan may also bear fruit, should bin Laden make it out of central Asia, said retired Rear Adm. Stephen Baker at the Center for Defense Information.

Some analysts note that bin Laden hasn't released a new videotape since the heavy U.S. bombing of Tora Bora, where officials are almost certain bin Laden was hiding until early December. His silence since suggests he's hurt, sick or hidden so deeply he cannot reach the outside world.

"If he can go on TV now, he can say, 'I beat the mighty United States. They tried to kill me and couldn't get me.' ... It's a very powerful message," Daalder said. "As each day goes by without another Usama videotape, it becomes more and more likely he's in bad shape."

White House spokesman Ari Fleischer said Friday that U.S. officials do not know whether bin Laden has died, but added, "I don't think the president would view that as an unwelcome event."

Several experts suggested the military will play less of an overt role in hunting bin Laden, with intelligence, diplomatic and police work returning to the fore.

"As the northern alliance asserts its control, it's going to become harder for us to do military operations in Afghanistan," Thompson said. "We can't do military operations at all in many of the surrounding countries."

In other developments:

• In Geneva, the United Nations refugee agency said it had relocated some 2,600 Afghan refugees from the Killi Faizo camp at Pakistan's border to camps farther inside Pakistan.

• Afghanistan's new ban on cultivating the opium poppy will take a bite out of the global narcotics trade, but only if farmers get aid as an incentive not to grow it, the Vienna-based U.N. Office for Drug Control and Crime Prevention said Thursday.

• Twenty Turkish troops left for Kabul as part of an advance party of peacekeepers, a military official said.

The Associated Press contributed to this report.