In her latest book, "The Wrong Enemy: America in Afghanistan 2001-2004", journalist Carlotta Gall has sourced her startling revelation to a retired Pakistani general Talat Masood.
"If allowed to proceed, the court cases may unravel some of the remaining mysteries of the Musharraf era," Gall writes in her book.
Musharraf is currently facing treason charges in a Pakistani court, besides other cases.
"One day as he sat at home in Islamabad, the retired general Talat Masood was watching an interview with Musharraf on television, Masood was struck by something the general said. Musharraf was talking about (Osama) bin Laden and as was often the case, he was talking too much," she writes.
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"I got a feeling that he knew," Gall said in her book that makes startling revelation and runs into over 300 pages.
Masood is the same general who after 9/11 urged Musharraf, the then president of Pakistan, to abandon his policy of supporting terrorism.
But Musharraf, according to the book, argued that he would "compartmentalise" the support between al-Qaeda and Kashmiri terrorists.