This seems like one of these incidents where Trump says something outlandish to be funny or elicit a reaction and the media runs with it like he is seriously going to do it:
Behind closed doors in 2017, President Donald Trump discussed the idea of using a nuclear weapon against North Korea and suggested he could blame a U.S. strike against the communist regime on another country, according to a new section of a book that details key events of his administration.
Trump’s alleged comments, reported for the first time in a new afterword to a book by New York Times Washington correspondent Michael Schmidt, came as tensions between the U.S. and North Korea’s Kim Jong-un escalated, alarming then-White House chief of staff John Kelly.
NBC News
You can read more at the link.