Trump says Tillerson is 'wasting his time' trying to negotiate with Kim Jong-un

U.S. President Donald Trump said on Sunday that he told the top U.S. diplomat not to waste his time trying to negotiate with North Korean leader Kim Jong-un.

"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, using his sarcastic nickname for Kim.

Trump's comment came the day after Tillerson disclosed that the United States was directly communicating with North Korea on its nuclear and missile programs but that Pyongyang had shown no interest in dialogue.

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

Tillerson said during a trip to China on Saturday that the U.S. was probing North Korea to see whether it is interested in dialogue and that it had multiple direct channels of communication with Pyongyang.

This was the first time the Trump administration acknowledged it was in direct communication with Pyongyang.

The disclosure came as Tillerson expressed hope for reducing tensions with North Korea, which is fast advancing toward its goal of developing a nuclear-tipped missile capable of hitting the U.S. mainland.

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"We are probing, so stay tuned," Tillerson told a small group of reporters during the China trip. "We ask: 'Would you like to talk?'"

He said the U.S. had "a couple of, three channels open to Pyongyang."

Asked for clarification about Trump's Sunday morning tweets about North Korea, a senior U.S. official played down the significance of the communication channels.

"At a time when North Korea is continuing its provocations, the president does not think now is the time to negotiate with them," the official told Reuters. 

The official also said to the extent that diplomatic channels exist between Washington and Pyongyang, they are aimed at securing the return of Americans detained by North Korea.

Trump has vacillated between direct personal attacks on the North Korean leader and a willingness to negotiate. After announcing new U.S. sanctions last month on North Korea, he also acknowledged diplomacy was still possible, asking: "Why not?"