President Donald Trump warned North Korea on Tuesday against its continued saber rattling, vowing to retaliate with fire and fury never before seen.

“North Korea best not make any more threats to the United States,” Trump told reporters Tuesday afternoon from his golf club in Bedminster, New Jersey, where he is staying as the White House undergoes renovations for much of this month.

Citing a confidential U.S. intelligence assessment, the Washington Post reported Tuesday that North Korea has successfully created a miniaturized nuclear warhead that can fit inside its missiles.

“They will be met with the fire and the fury like the world has never seen,” Trump said. “He has been very threatening beyond a normal state, and as I said they will be met with the fire and fury and, frankly, power, the likes of which this world has never seen before.”

The United Nations Security Council unanimously approved North Korea sanctions worth more than $1 billion over the weekend. Nikki Haley, the U.S. ambassador to the U.N., called it “the single largest economic sanctions package ever leveled against” Pyongyang.

North Korea, however, has vowed to continue strengthening its nuclear arsenal and threatened “thousands-fold” revenge against the U.S. The North Korean government labeled the sanctions a “violent infringement of its sovereignty” that it said was sparked by a “heinous plot to isolate and stifle” North Korea.

Trump has sought to pressure China into reining in North Korea. But the administration hasn’t been satisfied with China’s efforts. Trump tweeted late last month that he was “very disappointed in China,” who does “NOTHING for us with Korea, just talk.”

“We will no longer allow this to continue,” he pledged then, adding that “China could easily solve this problem!”

The president, however, more recently applauded both China and Russia for their U.N. votes but complained Monday that the so-called “Fake News Media will not talk about the importance of the” 15-0 vote despite widespread coverage of it.