Sen. John Kerry (D-Mass.), the chairman of the Senate Foreign Relations Committee, is uncertain whether the United States can stick to the July 2011 withdrawal date President Barack Obama has announced.

In an interview with PBS's Charlie Rose Thursday night, Kerry said drawing down troops without a stable Afghan government and security force could have horrible consequences.

"You can certainly do what you want to do in terms of the date, but it could wind up with very serious damaging consequences that we don't want to be responsible for," Kerry said. "So I do think there are legitimate questions about where we're going to be next summer. This is going to be a looming question in terms of our foreign policy and what we need to do."

Kerry said he had "personally cautioned against" setting a date, and suggested it will be harder for Afghans to beat back the Talbian than it was for Iraqis to defeat insurgents.

"In Iraq, first of all, you have to Sunni Awakening. We don't [have] a similar awakening, certainly not at this point in time, in Afghanistan," Kerry said.

The Massachusetts Democrat said things could turn around if operations in Kandahar are successful.

"If, on the other hand, that does not go well, I think, you know, we're going to have to go back to the drawing board," he said.