Gen. David Petraeus couldn't say he was confident that the U.S. can pull out of Afghanistan in 2014.
"I don't think there are any sure things in this kind of endeavor," he said in an exclusive interview with George Stephanopoulos on ABC's Good Morning America.
Winning in Afghanistan, Petraeus said, is "a bit different than, say, winning World War II or some conventional fight. This is not a case where you see the hill that you have to take, you take it -- you plant the flag and you go home to a victory parade. This is a much more complex endeavor than that, and it requires a very comprehensive approach."
Afghans are losing confidence in the U.S. and NATO presence in their country, according to a new poll conducted by The Washington Post, ABC News, the British Broadcasting Corp., and ARD television of Germany.
The poll, based on face-to-face interviews with a random sample of nearly 1,700 Afghan adults in all 34 of the country's provinces, shows a downturn from last year's results, despite the troop surge.
Only 36 percent of Afghans now express confidence in U.S. and NATO forces to provide security and stability in their area, down 12 points from last year and 31 points since 2006. In addition, more Afghans now say that the United States is playing a negative rather than a positive role in Afghanistan, 43 percent to 36 percent, a reversal from last year's figures.
Nevertheless, Petraeus said that military efforts in Afghanistan in the past several months have picked up, despite the Pentagon's latest six-month progress report on security and stability in Afghanistan, which says that the Taliban's reach is expanding.
"The data cutoff was in September," Petraeus said. "Some of our most important operations have really shown their achievement literally in the recent months."
When asked about a recent letter in which the Taliban claims to control more than 50 percent of Afghanistan, Petraeus's response was: "If you control so much of Afghanistan, why are all your senior leaders outside the country and never set foot inside the country?"
He argued that troops have "arrested the momentum that the Taliban have achieved in recent years, in many areas of the country, not all, but we have reversed it in some important areas, including right here in Kabul."
Petraeus conceded that "the Taliban is resilient," but said that a sustained commitment ensures that coalition troops are more skilled and experienced in the face of that resilience.