This article is by Thom Shanker, Peter Baker and Helene Cooper.

WASHINGTON  President Obama’s advisers are focusing on a strategy for Afghanistan aimed at protecting about 10 top population centers, administration officials said Tuesday, describing an approach that would stop short of an all-out assault on the Taliban while still seeking to nurture long-term stability.

Mr. Obama has yet to make a decision and has other options available to him, but as officials described it, the debate is no longer over whether to send more troops, but how many more will be needed. The question of how much of the country should fall under the direct protection of American and NATO forces will be central to deciding how many troops will be sent.

At the moment, the administration is looking at protecting Kabul, Kandahar, Mazar-i-Sharif, Kunduz, Herat, Jalalabad and a few other village clusters, officials said. The first of any new troops sent to Afghanistan would be assigned to Kandahar, the Taliban’s spiritual capital, seen as a center of gravity in pushing back insurgent advances.

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.