His comments came as the administration of Barack Obama, the US president, launched an all-out PR offensive to defend the war in Afghanistan, which is losing popularity with a war-weary American public.
Speaking on a Sunday morning television programme, Obama defended the war-effort, saying that the US was not trying to turn Afghanistan into a western-style democracy.
"What we're looking to do is difficult, very difficult, but it's a fairly modest goal, which is, don't allow terrorists to operate from this region," he said.
"That can be accomplished," he added. "We can stabilise Afghanistan sufficiently and we can get enough co-operation from Pakistan that we are not magnifying the threat against the homeland."
Opposition to the war is also growing from within sections of Obama's Democratic party.
Nancy Pelosi, the top Democrat in the House of Representatives, said that Americans wanted to see a more significant withdrawal than a figure of 2,000 troops floated by Joe Biden, the US vice-president.
"Well, I hope it is more than that," Pelosi told ABC, referring to the 2,000 figure offered by Biden. "I know it's not going to be turn out the lights and let's all go home on one day."
Many Democrats in the US congress recently broke ranks and voted against funding the nine-year-old war, which in July claimed the lives of 66 US troops in the deadliest month of the conflict so far.