"I just don’t want [him] to be able to say out loud the nuclear codes… because he is in a snit at three in the morning over something that somebody said about him, he decides he is going to obliterate the world," Schwartz said, adding, "I don’t think he is mentally stable."
In July, Schwartz, who co-wrote Trump’s 1987 memoir, ‘The Art of the Deal,’ issued a series of scathing personal critiques against the billionaire turned presidential candidate.
In response, Trump issued a cease and desist order and threatened further legal action against his former ghost-writer.
Schwartz added that the prospect of Trump controlling the US nuclear arsenal is "beyond frightening" and he is "nervous" over how a President Trump would match up against "any other world leader in a situation of conflict."
During the September 26 presidential debate, Trump argued that nuclear weapons represent the single greatest problem facing the world.