Al-Qaida leader Osama bin Laden may periodically slip back into Afghanistan from his remote hideout in neighboring Pakistan, a senior White House official says, adding a new twist to the mystery of the elusive terrorist''s whereabouts.

President Barack Obama''s national security adviser, James Jones, said bin Laden, believed hiding mainly in a rugged area of western Pakistan, may be spending some time in Afghanistan, where he was based while plotting the Sept. 11 attacks on the United States.

But Obama''s Pentagon chief, Robert Gates, said the U.S. has lacked good intelligence on bin Laden for a long time — "I think it has been years" — and did not confirm that he''d slipped into Afghanistan.

Jones and Gates spoke Sunday on separate TV interview shows as part of an administration effort to explain and defend Obama''s new Afghan war strategy, which Gates said includes a focus on preventing al-Qaida from again gaining a foothold inside Afghanistan. A concern is that the Taliban, if permitted to regain power in Kabul, could facilitate a return of al-Qaida''s leadership.