Former Afghan Ambassador claims US had prior knowledge of 9-11

In a memoir, the Afghan ambassador to Pakistan during 9-11 and ex-Guantanamo detainee Abdul Salam Zaeef claims that the United States had advanced foreknowledge of 9-11. It would be interesting to dig deeper into diplomatic exchanges between Kabul and Washington prior to 9-11. It would also be interesting to find out what exactly the US ambassador knew about the impending attack on America.