U.S. Secretary of State Hillary Clinton's said on Thursday it was "hard to believe" that no one in Pakistan's government knew where al Qaeda leaders were hiding, striking a new tone on a trip where Washington's credibility has come under attack.

Scores of al Qaeda leaders and their operatives, including Osama bin Laden, are believed to be in hiding in the rugged border territory that divides Pakistan and Afghanistan, but both countries routinely accuse the other of being the main sanctuary

"I find it hard to believe that nobody in your government knows where they are and couldn't get them if they really wanted to," she told a group of newspaper editors during a meeting in Lahore.

"Maybe they are not 'get-at-able'. I don't know," she said.