Faced with that reality, and the pressure of a self-imposed deadline to begin withdrawing troops by July 2011, the Obama administration is starting to count more heavily on the strategy of hunting down insurgents. The shift could change the nature of the war and potentially, in the view of some officials, hasten a political settlement with the Taliban.

Based on the American military experience in Iraq as well as Afghanistan, it is not clear that killing enemy fighters is sufficient by itself to cripple an insurgency. Still, commando raids over the last five months have taken more than 130 significant insurgents out of action, while interrogations of captured fighters have led to a fuller picture of the enemy, according to administration officials and diplomats.

American intelligence reporting has recently revealed growing examples of Taliban fighters who are fearful of moving into higher-level command positions because of these lethal operations, according to a senior American military officer who follows Afghanistan closely.

Judging that they have gained some leverage over the Taliban, American officials are now debating when to try to bring them to the negotiating table to end the fighting. Rattling the Taliban, officials said, may open the door to reconciling with them more quickly, even if the officials caution that the outreach is still deeply uncertain.