Carney would not say whether Obama worries that the killings increase security risks for Americans in Afghanistan. The United States has about 90,000 troops in the country; that number is scheduled to drop to 68,000 by the end of September.
Military movements were kept to a minimum Monday near the shooting site as commanders waited to see how the local population reacts, but there were no huge protests in the country. U.S. officials were worried that the Taliban would stoke public outrage this week in an attempt to turn the regular Friday prayer sessions into mass demonstrations.
"We're fully aware that this has the possibility of raising ire and emotions in a place where tensions are already running high," said State Department spokesman Mark Toner. "We would appeal for calm. "
Like other U.S. officials, Toner promised a thorough U.S. investigation and prosecution.
Even before the shootings, anti-Americanism was boiling in Afghanistan over U.S. troops burning Muslim holy books, including Qurans, last month on an American base. The burnings came to light soon after a video purporting to show four Marines urinating on Taliban corpses was posted on the Internet in January.
Americans, meanwhile, were outraged by the killings of American military advisers by Afghan soldiers. In the month of February, there were at least seven cases of Americans killed by Afghan soldiers, more than died in combat.
Pentagon press secretary George Little said the weekend house-by-house killing spree has not changed the U.S. approach to the war. Without offering any details about the killings, he stressed that it should be seen as an aberration.
"This is having no impact on the war effort at this time," he said. "No one should think that we are steering away from our partnership with the Afghan people, from our partnership with the Afghan security forces and from our commitment to prosecute the war effort."
But the strategy is already changing in small ways, with plans to shift combat operations to the Afghans earlier than once envisioned and some of the NATO partners largely recruited to the war by the U.S. increasingly entertaining an earlier exit.
Many war analysts predict a further telescoping of the withdrawal calendar after a NATO summit in May. Obama is hosting that meeting, in his adopted home town of Chicago.
Some of Obama's close advisers, including Vice President Joe Biden, opposed the large troop buildup Obama authorized in 2009. Obama has heard from advisers and analysts who remain ambivalent about whether a large U.S. "footprint" may do more harm than good, by presenting a target for Afghan anger and feeding the insurgent narrative that the Americans are colonial invaders.
The U.S. and Afghanistan are currently struggling to frame a security agreement that would govern how smaller numbers of U.S. forces can operate in the country after 2014, when the mission would narrow to hunting terrorists, conducting specialized military training and keeping an eye on neighboring Iran. The U.S. envisions a force of perhaps 20,000, according to military officials.
The U.S. role in civilian deaths has been a major sticking point in negotiations. Responding to massive public anger over the perceived indifference of the U.S. military to civilian deaths, Karzai wants greater Afghan control over "night raids." That's a catchall term for the military practice of entering and searching Afghan homes at night, in pursuit of militants and their supplies.
Kate Clark, of the Kabul-based Afghan Analysts Network, said the latest shootings are straining already tense relations.
"Relations are really irritable between the Americans and the Afghan government at the moment," Clark said. "This issue is just like a further irritant, like grit."
Associated Press writers Heidi Vogt in Kabul and Matthew Lee, Robert Burns, Julie Pace and Kimberly Dozier in Washington contributed to this report.
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