'Trump's nuclear button tweet to keep Kim on toes'

US Ambassador to the UN Nikki Haley said that President Donald Trump's "nuclear button" tweet warning Kim Jong-un about America's nuclear capabilities helps global security because it keeps the North Korean leader "on his toes", the media reported.

"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 told ABC News on Sunday.

"He can't sit there and imply that he's going to destroy the US without us reminding him of the facts and the reality that if you go there it's not us that's going to be destroyed, it's you," Haley said.

"I think that he (Trump) always has to keep Kim on his toes."

Haley told ABC News that Trump's tweets and actions help get the attention of world leaders who "see him as unpredictable".

"I don't think they know what the US is going to do at any given time."

The latest war of words between the two leaders began when Kim, in a New Year's speech, signalled his willingness to engage in talks with South Korea and claimed the entire US mainland was within range of North Korean missiles, reports CNN. 

"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 in a tweet, saying: "I too have a nuclear button, but it is a much bigger and more powerful one than his, and my button works!"

Also on Sunday, Central Intelligence Agency (CIA) Director Mike Pompeo made a similar argument about Trump's tweet in an interview on Fox News, saying that it was part of a strategy that broke with decades of unsuccessful US policy toward North Korea.

"That tweet is entirely consistent with what we're trying to communicate," Pompeo said. 

"We want the regime to understand that unlike before, we are intent on resolving this. And it is our firm conviction that resolving this diplomatically is the correct answer, but that this administration is prepared to do what it takes."