The response within the Obama administration has been a renewed debate on the so-called zero option — pulling out all American troops when the NATO combat mission here ends next year. Congress has also jumped into the fray with a Senate measure to withhold $5 in aid for every $1 Afghanistan charges the United States to move the equipment.

The poor poll numbers “reflect the noise that’s been out there for the last 60 days,” the general said, asserting that ground realities were better than portrayed in news reports. With the summer fighting season now almost half over, he said, Afghan forces “have proven very resilient.”

He described Al Qaeda, the reason the United States came to Afghanistan, as a shell of its former self, with only about 75 members in Afghanistan, and most of them too busy trying to stay alive to plan attacks in the West.

But keeping Al Qaeda on the margins would require American Special Operations Forces to remain after 2014 alongside regular troops focused on training, General Dunford said.

As in previous interviews, his focus was narrow, on Afghan security forces. He avoided talk of the debilitating level of corruption within the government, the weakening commitment to human rights among many Afghan officials, the faltering economy and uncertainty about next year’s presidential elections.

He did concede, however, that today “investing in Afghanistan, you could argue, was a gamble.”

But, if the elections are held and Afghan forces are able to keep the vote relatively secure, “it begins to be a risk like everywhere else,” he added.

By giving the Afghan Army and the police the tools needed to take on the Taliban, the United States “is providing the Afghan people with an opportunity to decide what kind of government they want to have.”