The newly appointed Director of National Intelligence Mike McConnell made the assertion about bin Laden and his No. 2 man, Ayman al Zawahri, in testimony before the Senate Armed Services Committee.
Referring to Pakistan's rugged tribal area, McConnell said "to the best of our knowledge that the senior leadership, No. 1 and No. 2, are there, and they are attempting to re-establish and rebuild and to establish training camps."
Until now, U.S. intelligence officials had declined to publicly identify, with such certainty, the location of bin Laden although he has long been suspected of hiding in Pakistan near the border with Afghanistan.
McConnell's testimony came the day after the CIA deputy director, Stephen R. Kappes, flew to Pakistan to confront President Pervez Musharaff with "compelling" evidence that new al Qaeda training camps were being established on Pakistani territory.
U.S. officials would not describe the evidence in any detail, but people in the intelligence community have speculated recently that the CIA may have obtained surveillance photos of either bin Laden or Zawahri in Pakistan.
McConnell's public testimony was followed by a closed, secret session with senators.