Ruppersberger expressed concern that Pakistan could become such an area. He said that "some of the Pakistani military and intelligence have relationships with those people who are fighting us."
The killings in Miran Shah, the main town in the North Waziristan tribal area, highlighted the challenges confronting the Pakistani military in the border region. The area is used by the country's fiercest enemy, the Pakistani Taliban, and by Afghan and Pakistani militants believed to be close to the government who are battling U.S. forces in Afghanistan.
The U.S. has repeatedly demanded that Pakistan launch an offensive in North Waziristan, especially against the so-called Haqqani network. Pakistan has promised to do so, but says its forces are stretched too thin fighting the Pakistani Taliban in other areas.
"Something has to be done, and it's in the offing," Pakistan Lt. Gen. Khalid Rabbani told the Associated Press on Monday. "North Waziristan is the only place left" that hasn't been the target of an operation, he said.
In Kabul, Whittington, the Maryland Guard general, directs the training and development of the Afghan army and national police. He said the security forces have grown from 270,000 in January 2011 to 340,000, and should hit the target of 350,000 this fall, ahead of schedule.
He said several developments indicate a growing strength within the Afghan forces: rising literacy rates among the soldiers, declining attrition, an increase in the number of Afghans leading the training, and the growing number of military doctors, nurses, police officers and logistics specialists.
"Their warrior culture translates to a good fighting force," Whittington said. "And now they're focused on not only the fighting piece of it but also the education of their warriors."
Since the attacks on Marchanti and other U.S. troops, the Afghan army and the interior ministry have increased training and vigilance to identify possible threats from within their ranks, an aide to Whittington said.
The security forces also have instituted a new eight-step vetting process that requires recruits to have a valid and verifiable identification card, a letter of endorsement or recommendation from their village elders, and a criminal background check.
Maryland National Guard Lt. Col. Charles Blomquist said the incidents "certainly … had an impact on how we conduct our business, our operations here."
"We stay vigilant, we rely a great deal on the training that we've received, and frankly the Afghans have also done the same," said Blomquist, who in civilian life is a prosecutor in Baltimore. "While it's maybe caused some slight delays on some things, I think overall we understand that there's perhaps a bigger mission that we need to focus on."
More than 3,100 Maryland National Guard members have served in Afghanistan since Sept. 11, 2001, some on multiple tours. Four have been killed.
In Kandahar, members of the 1297th Combat Sustainment Support Battalion — known as Task Force Raven — are nearing the end of year-long deployment receiving, organizing and shipping equipment through insurgent-infested territory to troops on the front lines in southern and western Afghanistan.
When what commanders say was unintentional mishandling of the Qurans at Bagram drew violent protests, troops were ordered to undergo cultural sensitivity training.
Spec. Louis Resto, a human resources specialist with the 1297th, doesn't handle the Quran in the course of his work. But he said it wouldn't have occurred to him that burning the book would offend anyone.
"It was a surprise to me," he said.
Lt. Col. Wheedon Gallagher said the incident did not affect the unit's mission — or the relationship with Afghan translators and truck drivers.
Blomquist, in Kabul, is on his second deployment to Afghanistan. He was in Kandahar in 2004 and 2005, and has seen progress since then.
"Here in Kabul, you have a very large metropolitan city with a very vibrant economy," he said. "There are traffic jams just as you would find in any other large capital city. There are people out on the streets, there's commerce going on. …
"I'm an optimistic person by nature, and I see that there has been progress. I would like to think that our involvement here is leading to a better life for the Afghans."
The Associated Press contributed to this article.