Suskind wrote: "The idea was to take the letter to Habbush and have him transcribe it in his own neat handwriting on a piece of Iraqi government stationery to make it look legitimate.
"CIA would then take the finished product to Baghdad and have someone release it to the media."
The letter, dated July 2001, surfaced in the UK in December 2003.
Suskind does not say who ordered it to be fabricated, but claims it came from the "highest reaches" of the White House.
Fratto and Tenet also rejected Suskind's allegation that the US had credible intelligence, before the 2003 invasion of Iraq, that Saddam did not possess weapons of mass destruction.
|Thousands have been killed since
the US invaded Iraq in 2003 [AFP]
The book also says a British intelligence official secretly met Habbush before the war in Amman, and that Habbush told him that Iraq had no weapons of mass destruction.
Fratto said US and other intelligence agencies believed Saddam possessed such weapons and that Saddam had tried to make his neighbours believe he had them.
In the end, no such weapons were found, undercutting Bush's main reason for the invasion of Iraq.
"We know now that those estimates were wrong, but they were the estimates we all relied on," Fratto said.
"Regardless, military force in Iraq was used because Saddam Hussein defiantly failed to comply with the 17 UN Security Council resolutions Iraq was subject to."