WASHINGTON - President Obama is prepared to accept some Taliban involvement in Afghanistan's political future and will determine how many more U.S. troops to send to the war based only on keeping al-Qaeda at bay, a senior administration official said yesterday.

A sharpened focus by Obama's team on fighting al-Qaeda above all other goals, while downgrading the emphasis on the Taliban, comes in the midst of an intensely debated administration review of the increasingly unpopular war.

Aides stress that the president's decision on specific troop levels and the other elements of a revamped approach is still at least two weeks away, and they say Obama has not tipped his hand in meetings that will continue at the White House today.

But the thinking emerging from the strategy-formulation portion of the debate offers a clue that Obama would be unlikely to favor a large military increase of the kind being advocated by the top U.S. commander in Afghanistan, Gen. Stanley McChrystal. McChrystal's troop request is said to include a range of options, from adding as few as 10,000 combat troops to - the general's strong preference - as many as 40,000.

Obama's developing strategy on the Taliban will "not tolerate their return to power," the senior official said in an interview. But the United States would fight only to keep the Taliban from retaking control of Afghanistan's central government - something it is now far from capable of - and from giving renewed sanctuary in Afghanistan to al-Qaeda, the official said.

The official is involved in the discussions and was authorized to speak about them but not to be identified by name because the review is still under way.

Bowing to the reality that the Taliban is too ingrained in Afghanistan's culture to be entirely defeated, the administration is prepared to accept some Taliban role in parts of Afghanistan, the official said. That could mean paving the way for Taliban members willing to renounce violence to participate in a central government - the kind of peace talks advocated by Afghan President Hamid Karzai to little receptiveness from the Taliban. It might even mean ceding some regions of the country to the Taliban.

Naming the enemy

Obama has talked positively about reaching out to moderates in the Taliban since he announced a new Afghanistan strategy in March. It would be akin to, though more complicated than, the successful efforts in Iraq to persuade Sunni Muslim insurgents to cooperate with U.S. forces against al-Qaeda there.

Obama has conferred nearly every day this week on the war, and continued that yesterday afternoon with Vice President Biden and Secretary of State Hillary Rodham Clinton.

On Wednesday, the eighth anniversary of the war launched by President George W. Bush after the Sept. 11 attacks, Obama and more than a dozen officials in his war council met for three hours to focus on Afghanistan's neighbor Pakistan. Another of those larger discussions - the fourth of five currently scheduled - is set for today, on Afghanistan. That meeting also could feature the group's first discussion of specific troop options.

In the first two of the sessions, which are taking place in the secure Situation Room in the White House basement, Obama kept returning, the official said, to one question for his advisers: Who is our adversary?

The answer was al-Qaeda, as it was back in March.

The primary aim

Amid changing circumstances in Afghanistan, the renewed determination has big implications for the war debate.

There now are no more than 100 al-Qaeda in Afghanistan, officials believe. Instead, the U.S. fight in Afghanistan is against the Taliban, now increasingly defined by the Obama team as distinct from al-Qaeda. While still dangerous, the Taliban is seen as an indigenous movement with almost entirely local and territorial aims and far less of a threat to the United States.

Obama's team believes some elements in the Taliban are aligned with al-Qaeda, with its transnational reach and aims of attacking the West, but probably not the majority and mostly for tactical rather than ideological reasons, the official said.

"They're not the same type of group," White House press secretary Robert Gibbs said. "It's certainly not backed up by any of the intelligence."

That leaves the primary aim in Afghanistan to deny al-Qaeda any ability to regroup there as it did when the Taliban was in power before the United States ousted it.

A focus on al-Qaeda is the driving force behind an approach being advocated by Biden as an alternative to the McChrystal recommendation for a fuller counterinsurgency effort inside Afghanistan.

Biden has argued for keeping the American force there around the 68,000 already authorized, including the 21,000 extra troops Obama ordered earlier this year, but significantly increasing the use of unmanned Predator drones and special forces for the kind of surgical antiterrorist strikes that have been successful in Pakistan, Somalia, and elsewhere.

There also is increasing reluctance among Obama's advisers to commit large additional numbers of troops because of concerns about the impact on already severely strained U.S. forces and the troubled Karzai government.

In Pakistan, the administration has been encouraged by the government's recent willingness to aggressively battle extremists inside its borders. Getting additional cooperation from Pakistan is delicate, as the anti-extremist operations remain extremely controversial there and the U.S.-backed civilian government in Islamabad is weak. But the administration sees opportunity there nonetheless.

Clinton has not revealed how she is leaning in the sessions, according to aides. While she is broadly supportive of building up troop levels - although not necessarily in the bigger numbers favored by McChrystal - she also believes economic and other civilian efforts must be prominent parts of the plan, said the aides, who spoke on condition of anonymity because they were not authorized to detail her views.

Also yesterday, the U.N. Security Council voted unanimously to extend authorization for NATO's 70,000-strong force in Afghanistan for a year.

Britain's U.N. ambassador, John Sawers, said the resolution's adoption by all 15 council members "underlines the extent of international support for the international effort there."