"If you don't understand what was happening, then you won't fix it for the next time, so I wanted to be very transparent about what went right and what didn't go right," Birx told "Good Morning America" in an interview Monday.
She described her response to the moment Trump raised the possibility of injecting disinfectant into people to treat COVID-19.
"I'm a pretty direct person, so I immediately went to his most senior staff ... and said this has to be reversed immediately. By the next morning, the president was saying it was a joke. But I think he knew by that even clearly that this was dangerous.
WATCH: Birx discusses phone call with Trump after COVID warning
She also noted that she had a pact with Dr. Anthony Fauci, former CDC director Robert Redfield and former FDA commissioner Stephen Hahn.
"If any one of the individuals were under so much pressure and they were fired, we would all leave together from the [White House Coronavirus] task force," she said.
Birx's book, "Silent Invasion: The Untold Story of The Trump Administration, COVID-19, and Preventing the Next Pandemic Before It's Too Late," will be published Tuesday, April 26.