President Donald Trump said Sunday it would be a waste of time trying to negotiate with North Korea over its nuclear program after it emerged the US had channels of contact with Pyongyang.

"I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man," Trump wrote on Twitter, referring to North Korean leader Kim Jong-Un.

"Save your energy Rex, we'll do what has to be done!"

Source: AFP