The original concept for the A-12 was for a high-supersonic platform which could be adapted to a variety of missions. There were planned or prototyped variants for interceptor and nuclear strike, and the names changed frequently while the program was in black development.

The A-12 was the CIA version of the SR-71, and was produced first. The SR-71 was opeerated by the USAF (and NASA which I think still has one or two).