Gen David Petraeus, the new commander of foreign forces in Afghanistan, said a 2011 target date to start withdrawing US troops will not bound him. (photo, from bbcimg.co.uk)
On NBC television, he said he reserved the right to tell president Obama whether the pull-out date was too early.
His announcement followed the deadliest month for US forces in July, since the Afghan conflict began in 2001.
Gen Petraeus also said the Afghan mission was tough and would remain so.
2011 was set by Obama as a target date to begin withdrawing US forces from Afghanistan in December 2009. At the same time he approved the deployment of 30,000 extra troops.
However Gen Petraeus said progress in Afghanistan only began this spring, when those troops arrived on the ground.
Gen Petraeus took over command of international forces in Afghanistan last month, after his predecessor, Gen Stanley McChrystal, was sacked for making disparaging remarks about the Obama administration in a magazine article.
Arresting al-Qaeda leader Osama bin Laden remains a primary goal, said Gen Petraeus. He described Bin Laden as an “iconic figure” for the insurgents, adding that his arrest remains a “very important task”.