The full interview between Bush and Matt Lauer -- the first of a publicity tour for his memoir, Decision Points, which is out today -- aired last night.
After Bush said waterboarding is legal because his Justice Department lawyers said it was, Lauer pressed him.
"Critics say that you got the Justice Department to give you the legal guidance and the legal memos that you wanted," he said. "Tom Kean, who was a former Republican co-chair of the 9/11 commission, said they got legal opinions they wanted from their own people."
"He obviously doesn't know. I hope Mr. Kean reads the book," Bush replied. "That's why I've written the book. He can, they can draw whatever conclusion they want. But I will tell you this. Using those techniques saved lives. My job is to protect America and I did."
Bush has also revealed that he personally gave the order to waterboard Khalid Sheikh Mohammed. He said, given the chance to do it over, he would make the same decision.
At one point, Lauer asked, "Would it be OK for a foreign country to waterboard an American citizen?"
"All I ask is that people read the book," Bush said. "And they can reach the same conclusion. If they'd have made the same decision I made or not."
Bush also spoke about his decision to go to war in Afghanistan.
"The decision to enforce new doctrine, which is if you harbor a terrorist, you're equally as guilty as the terrorist, was not that difficult to make," he said. "The hard decision is what to do after you have removed the Taliban. Our nation was ill equipped for nation building."
Asked if he could have imagined that the war would still be going on in 2010, Bush said, "I was hopeful that that would not be the case, but I was also mindful, Matt, of that and history tells us. Democracies take a while to develop, including our own."
On Hurricane Katrina, Bush said it "reinforced damage that was taking place" to his presidency.
"I had failed to get Congress to move on Social Security. Iraq was still very difficult. And so Katrina came along and it gave critics an opportunity to -- to kind of undermine the Presidency, I guess you could say," he said.