"It's not something he shies away from," Coates said. "If anyone wants to take issues with individual documents, they're welcome to."
In an ABC News exclusive, Rumsfeld will talk to ABC News' Diane Sawyer in his first television interview since leaving public service in November 2006.
Rumsfeld's memoir, "Known and Unknown," hits bookshelves on Feb. 8. The book coyly is named after Rumsfeld's famous 2002 quote explaining the lack of evidence on the Bush administration's claims that Iraq had weapons of mass destruction.
"Reports that say that something hasn't happened are always interesting to me, because, as we know, there are known knowns; there are things we know that we know," Rumsfeld said at the time. "There are known unknowns. That is to say, there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know."