WASHINGTON - After consistently insisting that Osama bin Laden has taken refuge in Pakistan's tribal areas, a top American official now says that the United States has not had any reliable intelligence on the whereabouts of the al-Qaeda chief for "years." That statement came from no less a person than the Pentagon chief, and analysts here wondered why American official had been so categorical in claiming that bin Laden was in Pakistan if there was no good intelligence available about him. Defence Secretary Gates's comments came in an interview with ABC's "This Week" news programme on Sunday, days after US demands that Pakistan step up efforts to hunt for bin Laden. "Well, we don't know for a fact where Osama bin Laden is. If we did, we'd go get him," Gates said. And Gates' colleague in the White House -- National security adviser James Jones -- added to the confusion, saying: The al-Qaeda leader still spends some time inside Afghanistan. When asked when U.S. officials last had "any good intelligence" on the whereabouts of the al-Qaida leader, Gates replied, "I think it's been years." He said he could not confirm a BBC report Friday that bin Laden may have been in Afghanistan. The report cited a detainee saying a trusted friend had told him he had seen bin Laden in Afghanistan early this year. Jones, a retired general, who appeared on CNN's "State of the Union, said the al-Qaeda leader is "sometimes on the Pakistani side of the border, sometimes on the Afghan side of the border." Jones said the US military and its allies in Afghanistan are "going to have to get after that" to ensure bin Laden is "once again on the run or captured or killed." Gates said the United States is "comfortable" with the safety of Pakistan's nuclear weapons, in part because of American-sponsored safety mechanisms. "We've given [the Pakistanis] assistance in improving their security arrangements over the past number of years Based on the information available to us that gives us the comfort," he told CBS News. Gates's comments were apparently aimed at assuaging American concerns about the possibility of nuclear stockpile falling in the wrong hands hands at a time of growing militant violence. Last week President Barack Obama asserted that "we know that al-Qaeda and other extremists seek nuclear weapons, and we have every reason to believe that they would use them". Those worries resurfaced after Friday's suicide attack on a mosque near the army headquarters in Rawalpindi, which killed 40 people including six serving officers.