Faced with an enemy that has virtually collapsed as an organized fighting force, the United States scaled back its bombing campaign in Afghanistan Thursday and began the tedious job of hunting down Usama bin Laden among the caves and tunnels dotting the country's southern landscape.

Video: Kabul Residents Cautiously Return to Normal Life

Carpet-bombing raids and airstrikes against Taliban front lines are giving way to more precise efforts — special operations troops questioning Taliban defectors and prisoners, dangling millions in reward money and hoping for a communications slip-up. Warplanes are focusing more on bombing mountain hideouts and caves where bin Laden might try to disappear.

The United States is bombing areas in the south and in the east, especially around Jalalabad, where bin Laden is known to have hideouts. "Bunker-buster" bombs can dig under the surface and explode in a tunnel. Fuel-air explosives can produce tremendous heat and suck out a cave or tunnel's oxygen.

Defectors and prisoners are probably the best hope for information on where bin Laden is now, said a former senior U.S. intelligence official with experience in South Asia. Even rumors or hints — about something such as a recent supply run to a cave, for example — could prove a breakthrough.

In addition, "It may very well be that money will talk at some point," Defense Secretary Donald Rumsfeld said Wednesday, referring to the millions in reward money the United States has offered.

Or, Taliban troops and commanders on the run might take fewer precautions with radios and phones, allowing U.S. eavesdropping aircraft to pick up communications and thus get hints to bin Laden's location.

U.S. special forces also have been watching roads in southern Afghanistan to see who passes by, Rumsfeld said, and "to stop people that they think ought to be stopped."

Bin Laden is believed to move from cave to cave — some a three days' walk into the mountains — with only a group of highly trusted aides.

Bin Laden Alive and Safe

Taliban officials said bin Laden and their own supreme leader, Mullah Mohammad Omar, were safe and in Afghanistan, the Afghan Islamic Press said.

"They are in Afghanistan and there has been no harm to them," the private Pakistan-based AIP quoted Taliban spokesman Mullah Abdullah as saying.

Asked whether the beleaguered Taliban were ready to strike a compromise with the United States on handing over bin Laden, Abdullah said: "There is no change in our position on the issue of Usama." 

Taliban Appear to Be Fleeing Stronghold of Kandahar

With opposition forces reported to be taking over Kandahar's airport, the Taliban are giving up hope of defending the city and are escaping into the mountains, Pentagon sources told Fox News.

The U.S. effort to foster dissent among Pashtun leaders has persuaded some of the groups to rise up, although tribes are acting on their own volition, a U.S. official said.

Taliban supporters say the withdrawal from urban areas throughout Afghanistan is a strategy that will allow the militia and its allies to wage a guerrilla war from Kandahar's rugged mountains and caves.

Pentagon officials now believe that two-thirds of Afghanistan is under the control of anti-Taliban forces, including opposition forces in the far west of the country.

Meanwhile, Northern Alliance officials in Kabul quickly returned Wednesday to the government offices they abandoned in 1996 when the Taliban drove them from power.

Officials portrayed the takeover of key ministries, such as defense and interior, as temporary, and said they support a U.N.-supervised political settlement in which all ethnic groups would be represented.

Former King: Choose Your Own Destiny

Afghanistan's former king, Mohammed Zaher Shah, urged the Afghan people to unite and freely choose their own destiny in a statement made public Wednesday to be broadcast by radio in his homeland. 

Zaher Shah, who has lived in exile in Italy since his ouster in 1973, called for "solidarity, unity and cooperation" and said the holding of a meeting of tribal leaders was the only way to bring a government representing all Afghan factions. 

Aides to the former king said he intended to return to Afghanistan soon to serve as a symbol of national unity, though Zaher Shah has said he does not seek to regain the throne.

Fox News' Bret Baier and The Associated Press contributed to this report.