U.S. Ambassador to the U.N. Nikki Haley has defended President Donald Trump over his recent "nuclear button" tweet, denying that it hurts Washington's credibility with its allies and calling such moves necessary to keep North Korean leader Kim Jong Un "on his toes."

Haley, speaking Sunday on ABC's "This Week," was responding to a question about Kim's New Year's Day address, in which he claimed that the entire U.S. was in range of North Korean missiles and said that "the nuclear button is always on the desk of my office. They should accurately be aware that this is not a threat but a reality."

Trump responded with a tweet laying into Kim: "Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!"