The United States will launch a new effort to track down Osama bin Laden who is believed to be hiding in the mountains along the Afghan-Pakistan border, a senior US official said on Sunday.
Intelligence reports suggest the al-Qaeda chief "is somewhere inside north Waziristan, sometimes on the Pakistani side of the border, sometimes on the Afghan side of the border," said national security adviser James Jones.
Asked if President Barack Obama's administration planned a fresh attempt to go after al-Qaeda's leader, Jones said: "I think so."
Bin Laden was a "very important symbol of what al-Qaeda stands for" and it was crucial to make sure he was on the run or captured, Jones, a retired Marine general, told CNN's "State of the Union" program.
His comment that Bin Laden sometimes crossed to the Afghan side of the mountainous border contrasted with previous accounts from US officials that suggested the al-Qaeda chief was hiding in Pakistan.
Despite the vow to track down Bin Laden, Defense Secretary Robert Gates said on Sunday that intelligence agencies did not know where the al-Qaeda leader was and had lacked reliable information on his whereabouts for years.
"We don't know for a fact where Osama bin Laden is. If we did, we'd go get him," Gates, a former CIA director, told ABC News' "This Week."
The al-Qaeda network leader is seen as the chief mastermind of the attacks of September 11, 2001 on New York and Washington that killed nearly 3,000 people.
US government officials have named Bin Laden and the al-Qaeda network as the prime suspects in the attacks and offered a 50 million dollar reward, but for more than eight years Bin Laden has avoided capture.
Secretary of State Hillary Clinton said Sunday it was "important" to capture or kill Bin Laden and other Al-Qaeda figures but told NBC that "certainly you can make enormous progress absent (without) that."
A Senate report released last week said Bin Laden was "within the grasp" of American forces in late 2001 in Afghanistan but escaped because then-defense secretary Donald Rumsfeld rejected calls for reinforcements.