The Bush administration plans to give the Northern Alliance of Afghan opposition forces at least several more weeks to make progress in toppling the ruling Taliban regime, a senior defense official said Monday. After that time, the United States may have to consider committing its own ground forces.

Rear Adm. John Stufflebeem, the Pentagon's designated spokesman on military operations in Afghanistan, said much of the U.S. bombing is designed to soften up the Taliban for the Northern Alliance.

Stufflebeem said the bombing was "preparing the battlefield" for future action by opposition forces, who are loosely aligned, ill-equipped and outnumbered by the Taliban.

U.S. officials have made clear that military action is aimed at supporting the Northern Alliance, but they have not specified how long the United States will wait for them to take the offensive. An even harder issue is determining whether the opposition can win.

Stufflebeem expressed confidence the Northern Alliance will make a move, but he could not predict when.

"It would be incorrect for us to assume that, after so many missions of prepping that particular battlefield, that we would say, 'It's ready for you to go; you should be going now.'" he said.

"They've got to make that determination for themselves on the ground, and we are sure that they will. And once they're comfortable, we will attempt to help them again in any way that we can."

Secretary of State Colin Powell, in an interview with Egyptian television, said no decision has been made on using U.S. ground forces in combat.

The troops there are are working with anti-Taliban groups to make them more capable. "We think that in the weeks ahead the opposition forces will become more effective with the benefit of U.S. support and the support of others," Powell said.

U.S. Scouting Bases in the Region

In the meantime, the U.S. military is seeking access to more bases on Afghanistan's periphery to accelerate its bombing campaign, expand humanitarian aid missions and speed the delivery of supplies to opposition forces.

Stufflebeem confirmed that a U.S. military team is in Tajikistan, on Afghanistan's northern border, to assess the feasibility of using any of three former Soviet military bases.

Those bases — and others in neighboring Uzbekistan and elsewhere in the area — could be used to accelerate the delivery of arms, food and other supplies to the Northern Alliance, another official said.

The bases also could serve as a staging area for U.S. cargo aircraft delivering humanitarian aid to Afghans and U.S. Air Force fighter-bombers targeting Taliban troops and hide-outs. Up to now, the vast majority of U.S. combat flights have originated from aircraft carriers in the Arabian Sea. U.S. long-range bombers have flown missions from an island in the Indian Ocean and from the United States.

"There's a whole host of reasons why having airfields closer to Afghanistan is good," Stufflebeem said. He cited as examples: less need for midair refueling, quicker response time for strike missions based on timely intelligence information, and a faster cycle of missions resupplying the Northern Alliance.

In addition to the former Soviet bases, the United States is interested in bases inside Afghanistan.

A small team of U.S. military personnel landed at a new airstrip in Golbahar, Afghanistan, in the northern end of the Shomali plain "to help coordinate efforts in the war," opposition interior minister Yunis Qanoni told The Associated Press on Monday.

He said the men arrived Sunday from Tajikistan's capital, Dushanbe, in a small twin-engine plane. They were to study the new dirt landing strip to see if it can handle the delivery of supplies for Northern Alliance forces.

The United States also is interested in gaining use of Bagram air base, north of Kabul, a defense official said Monday. The Taliban controls that base, but if the Northern Alliance launched a successful offensive in that direction, it might gain Bagram.

Rumsfeld: Special Forces Troops Doubled Over Weekend

In New Delhi, Defense Secretary Donald H. Rumsfeld told a news conference with his Indian counterpart, George Fernandes, that U.S. bombing is "improving every day," helped by additional teams of U.S. special forces soldiers who are providing targeting information for strike aircraft.

Rumsfeld was returning to Washington after visiting Pakistan, Tajikistan, Uzbekistan and India.

In comments Monday to reporters flying with him, Rumsfeld said that over the weekend, the number of U.S. special forces troops on the ground in Afghanistan had gone "2 times above what we had." He gave no figures, but officials in Washington said the total is still less than 100.

Rumsfeld said those special forces troops, who are working with Northern Alliance forces and directing U.S. air strikes, are now at four or more locations. They previously were at two locations.

"That will accrue to our advantage over the coming period," he said, according to a transcript released at the Pentagon.

The Associated Press contributed to this report.