On Sunday, he wrote on Twitter that he had asked South Korean President Moon Jae-in "how Rocket Man is doing."

Haley said the new nickname "worked."

"I was talking to a president of an African country yesterday, and he actually cited 'Rocket Man' back to me," she said in an interview on ABC. "This is a way of getting people to talk about him, but every other international community now is referring to him as Rocket Man."

She also defended Trump's fiery address during which he threatened to "totally destroy" North Korea.

"I think what you saw was the president responding to North Korea's ballistic missile testing, their nuclear bomb tests, and their threats that they're going to reduce the United States to ashes, as well as destroy Japan," Haley said in a separate interview on NBC.

The president has to "speak up" on behalf of Americans and on behalf of US allies and friends, she argued.

Responding to concerns the heated rhetoric could push North Korea to make a miscalculation, Haley said US has exhausted all other options, including sanctions and dialogue.

"We have reduced all our diplomatic measures as much as possible to try and see how we can get to him (Kim)," she said. (Yonhap)