But military planners are also pressing for enough troops to safeguard major agricultural areas, like the hotly contested Helmand River valley, as well as regional highways essential to the economy — tasks that would require significantly more reinforcements beyond the 21,000 deployed by Mr. Obama this year…

But such a strategy would be open to complaints that American and allied forces were in effect giving insurgents free rein across large parts of the nation, allowing the Taliban to establish ministates with training camps that could be used by Al Qaeda…

Military officers said that they would maintain pressure on insurgents in remote regions by using surveillance drones and reports from people in the field to find pockets of Taliban fighters and to guide attacks, in particular by Special Operations forces…

A strategy of protecting major Afghan population centers would be “McChrystal for the city, Biden for the country,” as one administration official put it.