Oct. 1 (UPI) -- President Donald Trump said Sunday it is a "waste of time" to negotiate with North Korea, one day after his secretary of state said the U.S. had "lines of communication" in an effort to diffuse tension.
"I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man ... " Trump posted on Twitter on Sunday morning. "Save your energy Rex, we'll do what has to be done!"
Then 4 1/2 hours later, he posted: "Being nice to Rocket Man hasn't worked in 25 years, why would it work now? Clinton failed, Bush failed, and Obama failed. I won't fail."
No official diplomatic relationship exists between Washington and Pyongyang.
During a trip to Beijing, China, a key ally of North Korea, Tillerson told reporters: "We ask: Would you like to talk? We have lines of communications to Pyongyang. We're not in a dark situation, a blackout. We have a couple, three channels open to Pyongyang."
But North Korea hasn't spoken to American diplomats.
"Despite assurances that the United States is not interested in promoting the collapse of the current regime, pursuing regime change, accelerating reunification of the peninsula or mobilizing forces north of the DMZ, North Korean officials have shown no indication that they are interested in or are ready for talks regarding denuclearization, State Department spokeswoman Heather Nauert said Saturday in a statement.
On Sunday, Nauert tweeted: "Diplomatic channels are open for #KimJongUn for now. They won't be open forever."
Threats have been escalating between Trump and North Korean leader Kim Jong-Un for months. Trump has called Kim "Rocket man" and Kim has described Trump as a "mentally deranged U.S. dotard."
After a missile test, Trump in August said "all options are on the table" in response to the regime's "threatening and destabilizing actions."
Kim has threatened military against against Guam, a U.S. territory, and in early September announced it successfully tested a hydrogen nuclear bomb that can be loaded onto an intercontinental ballistic missile and is capable of reaching the U.S. mainland.
On Sept. 19, Trump during a speech at the United Nations in New York threatened to "destroy North Korea" if it is threatened.
The United Nations has repeatedly sanctioned North Korea.
"Diplomacy not a favor we dispense but a critical national security tool for ourselves," tweeted Richard N. Haass, president of the Council on Foreign Relations. "Potus truly misguided here-& SecState should resign."
"I see no benefit whatsoever of doing this," Ilan Goldenberg, a senior fellow at the Center for a New American Security told Politico. "It's just more Trump irresponsibly escalating for no real reason."