American jets prowled the skies in southern Afghanistan early Wednesday, seeking out convoys of Taliban fighters retreating toward their last major stronghold of Kandahar, one day after opposition troops took control of at least half the country and American commandos landed in the capital.

Video: Northern Alliance Takes Kabul

Defense Secretary Donald Rumsfeld, while insisting that the war on terror will go on long after the fight in Afghanistan is over, painted a cautious but upbeat picture at a Tuesday press conference on the progress made against the Taliban so far. Taliban troops fleeing the U.S. assault as well as the terrorists they harbor will be hunted down wherever they hide, Rumsfeld said.

"We're going to get them," he said. "I doubt that they'll find peace, wherever they select."

Other U.S. officials have been less cautious. One, speaking on condition of anonymity, said the Taliban are collapsing in disarray. Many of their field commanders, lacking supplies, reinforcements or meaningful contact with the senior leadership, have simply fled. Some are switching sides to the Northern Alliance.

U.S. intelligence believes Taliban forces are also abandoning Konduz, their last stronghold in northern Afghanistan, and are moving south, through alliance-controlled territory, the official said.

Rumsfeld said a small number of U.S. troops are in Kabul, helping the Northern Alliance rebels who drove out the Taliban early Tuesday. Another contingent is operating in the Taliban-controlled south. U.S. troops are also working with Northern Alliance soldiers in the north, where only pockets of Taliban resistance remain.

Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said Northern Alliance commanders have effectively cut Afghanistan into two areas of control.

They "have taken all northern provinces," he said, leaving the Taliban in control only in the south — and even there they were facing pressure from bombing and local resistance. Myers said the Taliban retreat "appears to be more disorganized than organized."

U.S. planes were pursuing them. "We are looking for Taliban on the move," he said, but "the trick is trying to differentiate between Taliban and other people who may be leaving those locations."

Rumsfeld said the U.S. military hoped to open a land bridge into Afghanistan from neighboring Uzbekistan and repair airfields north of Kabul and near Mazar-e-Sharif to permit large-scale humanitarian aid to come in. It also would give U.S. forces greater ability to launch attacks inside the country.

White House spokesman Ari Fleischer said President Bush "is very pleased with the progress of the war and with the latest developments."

The U.S. bombing campaign continued apace, and the Pentagon approved a request by the U.S. war commander to send another three-ship Amphibious Ready Group from the Mediterranean Sea to the Arabian Sea.

The group, which has 2,100 Marines on board, would join a similar number aboard the USS Pelileu. The two Marine groups are capable of a variety of missions, including airborne assaults.

Wednesday, for the first time in weeks, Kabul residents awoke after a night free of U.S. bombing raids. Triumphant Northern Alliance fighters patrolled the streets, and their leaders said the Taliban was losing its grip on its southern strongholds.

U.S. warplanes, whose bombs helped force the Islamic militia to abandon Kabul to the Northern Alliance early Tuesday, kept up the pressure with more air raids outside the capital.

American aircraft bombed the airport and military installations around the eastern city of Jalalabad at least six times overnight and early in the morning, the Pakistan-based Afghan Islamic Press reported.

Citing an unidentified Taliban official, the agency also said warplanes attacked a military base in Khost, six miles from the Pakistan border.

The Taliban have apparently retreated south, to their mountainous stronghold of Kandahar, where the Islamic militia first emerged in 1996. Supporters say the Taliban's withdrawal from urban areas is a strategy that will allow the militia and its allies to wage a guerrilla war from inside Kandahar's caves.

The Associated Press contributed to this report.