US bombers have hit a compound south of Tora Bora targeted three years ago as Osama bin Laden's headquarters.
The complex, in the Khost region of Afghanistan, was attacked by B1 bombers and F18 strike aircraft after reports of "significant activity".
The bombing is the first of the new year and comes after days of air patrols across Afghan skies.
The complex is the same one which former president Mr Bill Clinton ordered to be struck in August 1998, following the al-Qaeda bombing of the US embassies in Kenya and Tanzania.
US General Myers refused to discuss who was believed to be at the complex when it was struck, but said it was used by al-Qaeda.
And US Defence Secretary Mr Donald Rumsfeld said the use of bombers is now a last resort in Afghanistan.
"If you look at the amount of bombing we have been doing in the last week or so, it is obvious that is not our first choice," he said.
AP