President Trump on Sunday said he wouldn't fail in dealing with the North Korean threat.

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

"Clinton failed, Bush failed, and Obama failed. I won't fail," he promised, referring to past presidents.

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. — Donald J. Trump (@realDonaldTrump) October 1, 2017

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His 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 the U.S. was in direct contact with North Korean officials, even though there is no official diplomatic relationship between Washington and Pyongyang.

State Department spokeswoman Heather Nauert said North Korea showed no interest in negotiating on matters related to its nuclear weapons program.

Earlier Sunday, Trump said he told Tillerson it was a waste of time to try 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 said.

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

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

Trump's tweets on North Korea come during a weekend when his administration is under increasingly critical scrutiny for the federal response to disaster relief in Puerto Rico.

Trump tweeted Sunday afternoon on his way to Liberty National Golf Course, in Jersey City, N.J., where he will attend the Presidents Cup golf tournament.