U.S. Secretary of State Rex Tillerson said on Sunday that he would continue his diplomatic efforts vis-a-vis North Korea as long possible.

"Those diplomatic efforts will continue until the first bomb drops," Tillerson told CNN in an interview.

He stressed that prioritizing diplomacy to try to curb North Korea's nuclear ambitions is President Donald Trump's preferred avenue, despite the president's recent tweets suggesting he thought otherwise.

"The president has also made clear to me that he wants this solved diplomatically," Tillerson said. "He is not seeking to go to war."

Tillerson acknowledged several weeks ago that the United States was directly communicating with North Korea on its nuclear and missile programs.

"We are probing so stay tuned," Tillerson told a group of reporters in Beijing, adding, "We ask: 'Would you like to talk?' We have lines of communications to Pyongyang. We're not in a dark situation, a blackout."

Shortly after Tillerson's comments, Trump wrote on Twitter that he thought Tillerson was "wasting his time" trying to negotiate with North Korea.

"I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man...Save your energy Rex, we'll do what has to be done!" the president tweeted.

Trump subsequently vowed that he would not fail as his predecessors did in trying to stop North Korea’s nuclear program.

Asked if Trump's tweets undermined his diplomatic efforts, Tillerson told CNN that connections between U.S. and Chinese leaders were close and that the Chinese "are not confused in any way" about US policy toward North Korea.

As for Trump's tweets themselves, Tillerson said the President made the statements he did to try to "motivate action."

U.S. Defense Secretary James Mattis has expressed support for Tillerson's effort to find a diplomatic solution to the crisis with North Korea, but last week instructed the army to have military options ready in case the diplomatic efforts fail.