As U.S. planes run out of the best bombing targets in Afghanistan, the military response to terrorism is moving into a much more delicate phase: trying to roust the Al Qaeda terrorists from their hideouts and topple the Taliban regime sheltering them. 

All of the options have risks.

—Sending in small teams of special forces soldiers to hunt down terrorist and Taliban leaders might not be enough to eliminate all of them from Afghanistan.

—Dispatching a larger force of ground troops raises the possibility of American casualties and erosion of support from Muslim allies.

—Helping anti-Taliban rebels means getting involved with a fractious group of warlords, some of whom are accused of corruption and atrocities of their own.

Those risks should not prevent America from pursuing its goals in the anti-terrorism campaign, said Richard Perle, who was a senior Defense Department official in the Reagan administration.

``There's always the risk that you will fail, that after this is all over the Taliban will not only be in power but may even lay claim to being stronger than before,'' said Perle, now at the American Enterprise Institute, a conservative-leaning think tank.

``There's even the possibility that in the ensuing chaos that someone will rise to power who is as bad, maybe in a different way. But if you allow yourself to be deterred from things that need to be done in the short term because you're worried about the long term, you can be paralyzed.''

Pentagon officials indicate they're aware of the risks and realities of the situation. Although he has been mum about what form the next phase of military action will take, Defense Secretary Donald H. Rumsfeld has said the military mission will include more than bombing.

``It's unlikely that the airstrikes will rock the Taliban back on their heels,'' Rumsfeld said last week.

Special forces are almost certain to play a key role, military officials have said. That could include training and equipping rebel forces or making commando raids to capture or kill Taliban or Al Qaeda leaders.

But the Taliban forces are larger and better equipped than the rebels, and many of the Taliban fighters, including thousands of foreigners, probably would fight to the death, U.S. officials and outside experts said.

The airstrikes in recent days have moved from stationary command targets like airfields and headquarters to troop concentrations and supplies. Part of the strategy could be to disrupt the Taliban enough so that it will be vulnerable to the rebels.

Once the Taliban falls, Al Qaeda would disintegrate — kill the host, the theory goes, and the parasite of Al Qaeda would die, too.

While the U.S.-led attacks have not been coordinated with the rebels for political reasons, the anti-Taliban forces have provided information about targets, said Maj. Gen. Henry P. Osman, a top Pentagon planner.

A series of commando raids that come up empty-handed could encourage some countries to drop out of the anti-terrorism alliance. Working with the anti-Taliban forces risks alienating Pakistan, which supported the Taliban in the past and does not want to see the rebel alliance take power.

While such concerns are political, they do affect military planning, said retired Gen. Fred Woerner, former head of the U.S. Southern Command.

``The president is not a free agent on this. Everything he is planning on doing comes with some cost, domestically and internationally,'' Woerner said.

Some analysts say defeating the hard-core Taliban fighters could require American infantry soldiers to enter Afghanistan. Whether the United States will send regular ground forces into Afghanistan is in doubt, however.

``As to whether or not we will put troops on the ground, I'm not going to tell you,'' Bush said last Tuesday.

A ground strategy has serious risks — of accidentally killing civilians, of piling up U.S. casualties and of alienating other countries. A large number of dead civilians could cause internal unrest in Pakistan and other Muslim countries backing the U.S. mission.

Taliban claims of hundreds of civilians killed — as well as the Pentagon's admission Saturday that a guided bomb missed by a mile, hitting a residential area — have helped fuel anti-American protests in Pakistan and elsewhere.

``As long as it's focused over a short period of time, and as long as there aren't any major civilian casualties, it becomes manageable politically,'' said Clovis Maksoud, a former United Nations representative for the League of Arab States. ``More casualties would create an escalation of not only protests but confrontation with the governments that are supporting the United States.''

A political and diplomatic solution is what Afghanistan needs to start rebuilding and move to a stable government that does not support terrorism, said strategist Harlan Ullman at the private Center for Strategic and International Studies.

``Military force can blow things up and kill people, and its threat can affect the will of an adversary, but if you're looking for a long-term solution, it's got to be by other means,'' Ullman said.