A State Department spokeswoman said Sunday that diplomatic channels are open for North Korea's leader "for now."

"#DPRK will not obtain a nuclear capability. Whether through diplomacy or force is up to the regime @StateDept," spokeswoman Heather Nauert tweeted.

"Diplomatic channels are open for #KimJongUn for now. They won't be open forever," she added, referring to North Korea's leader, Kim Jong Un.

#DPRK will not obtain a nuclear capability. Whether through diplomacy or force is up to the regime @StateDept — Heather Nauert (@statedeptspox) October 1, 2017

Diplomatic channels are open for #KimJongUn for now. They won't be open forever @StateDept @potus — Heather Nauert (@statedeptspox) October 1, 2017

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Her comments come after Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE said Saturday that the U.S. was in direct contact with North Korean officials.

President Trump, however, tweeted that he told Tillerson that it was a waste of time trying to negotiate with North Korea's leader.

"I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man," the president tweeted.

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

Trump later tweeted that "being nice" to North Korea's leader has never worked in the past.

"Being nice to Rocket Man hasn't worked in 25 years, why would it work now?" Trump said, using his own nickname for Kim Jong Un.

"Clinton failed, Bush failed, and Obama failed. I won't fail."

Tensions between the U.S. and North Korea intensified this summer after Pyongyang tested a series of intercontinental ballistic missiles, defying the international community.