National Security Adviser Henry Kissinger: In the Laotian thing, we killed about ten, fifteen [thousand].
Nixon: See, the attack in the North [Vietnam] that we have in mind … power plants, whatever’s left – POL [petroleum], the docks … And, I still think we ought to take the dikes out now. Will that drown people?
Kissinger: About two hundred thousand people.
Nixon: No, no, no, I’d rather use the nuclear bomb. Have you got that, Henry?
Kissinger: That, I think, would just be too much.
Nixon: The nuclear bomb, does that bother you? … I just want you to think big, Henry, for Christsakes.
White House tape recordings, April 25, 1972. Source.