Washington (CNN) — US ambassador to the UN Nikki Haley says President Trump’s tweet warning North Korean leader Kim Jong Un about US nuclear…

Washington (CNN) — US ambassador to the UN Nikki Haley says President Trump’s tweet warning North Korean leader Kim Jong Un about US nuclear capabilities helps global security because it keeps Kim "on his toes."

"We want to always remind them we can destroy you, too, so be very cautious and careful with your words and what you do," Haley said Sunday on ABC’s "This Week."

The latest war of words between the two leaders began when Kim, in a New Year’s speech, signaled his willingness to engage in talks with South Korea and claimed the entire US mainland was within range of North Korean missiles. "The nuclear button is always on the desk of my office," he said. "They should accurately be aware that this is not a threat but a reality."

Trump responded via Twitter, saying, "I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!"

Critics said Trump’s tweet was too flippant and raised new questions about whether he understands the gravity of a potential nuclear war. But Haley said Sunday that Trump’s wording was an appropriate response to Kim’s statement