Originally Posted by
tartare
The very interesting thing I read somewhere recently (I will try to find the reference) was that the Japanese were secretly attempting to open back channel war ending negotiations with the US immediately prior to the bombs being dropped. And the US knew that - having decrypted cypher messages. There was an implication (I think it might have been in the Oppenheimer biography) that atom bombing Japan would be proof of the technology working.
It's quite a stretch to believe that the Roosevelt and then Truman Administrations would have been receptive to diplomatic overtures such as you have described, with the sounds of Tokyo Rose still reverberating in the Pacific Theater and the casualties of island- hopping still searing the public mind, right next to the Death March and Divine Wind (kamikaze).
Though I didn't read it completely, perhaps your source is
Hiroshima: The World's Bomb (Andrew Rotter 2008)? The book's opening chapter(s) recount the development of aviation from its earliest and, iirc, the nexus of that development to efforts to build an atomic weapon.