It was thought Bin Laden was hiding along the Pakistan-Afghan border
The US has had no reliable information on the whereabouts of al-Qaeda leader Osama Bin Laden in years, US Defence Secretary Robert Gates has admitted.
Mr Gates told ABC News in remarks broadcast on Sunday: "Well, we don't know for a fact where Osama Bin Laden is. If we did, we'd go get him."
A Taliban detainee in Pakistan told the BBC last week that he had information Bin Laden was in Afghanistan this year.
However, Mr Gates said he could not confirm that information.
When asked by ABC's This Week programme when the US last had any good intelligence on the whereabouts of the al-Qaeda leader, Mr Gates said: "I think it's been years."
He could not confirm the details of the Taliban detainee, who claimed to have met Osama Bin Laden numerous times before 9/11.
The detainee said that in January or February he met a trusted contact who had seen Bin Laden about 15 to 20 days earlier in Afghanistan.
Bin Laden had previously been thought to be on the Pakistan side of the border with Afghanistan.
But the detainee said that militants were avoiding Pakistani territory because of the risk of US drone attacks.
The detainee said Bin Laden was well.
Mr Gates' comments came after US President Barack Obama announced a decision this week to send 30,000 more US troops to Afghanistan.
He recalled that the US was fighting there in response to the 9/11 attacks against America by al-Qaeda, and had made the decision to invade "only after the Taliban refused to turn over Osama Bin Laden".
Mr Obama said al-Qaeda leaders had escaped into Pakistan in 2001 and 2002 and had been able to "retain their safe-havens along the border".
A recent US Senate report prepared by the Foreign Relations Committee Democratic staff concluded that Bin Laden had been "within our grasp" in Afghanistan in late 2001.
But it said that at the time, calls for US reinforcements had been rejected, allowing the al-Qaeda leader to "walk unmolested" into Pakistan's unregulated tribal areas.
Last week, UK Prime Minister Gordon Brown called on Pakistan to do more to find Mr Bin Laden.
"We've got to ask ourselves why, eight years after September the 11th, nobody has been able to spot or detain or get close to Osama bin Laden, nobody's been able to get close to [Ayman al-] Zawahiri, the number two in al-Qaeda," he said.
Pakistani Prime Minister Yousuf Raza Gilani responded by saying he did not think Bin Laden was in Pakistan, and that his country had yet to be given any "credible or actionable information" by the US on Bin Laden.