"North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the US It won't happen!" Trump tweeted.
Trump quickly followed that up with a charge that China was doing nothing to help the US cope with the rogue nation.
"China has been taking out massive amounts of money & wealth from the U.S. in totally one-sided trade, but won't help with North Korea. Nice!" Trump wrote.
The US President-elect launched his verbal missiles after the 32-year-old North Korean leader declared in a televised New Year's Day speech that his military is on the brink of testing its first intercontinental ballistic missile: a rocket that can be equipped with nuclear weapons and is powerful enough to reach any part of the US.
Jeffrey Lewis, director of the East Asia Nonproliferation Program (EANP) said Trump's tweets were "foolish, but probably harmless."
"I think North Korea will probably test the KN-08 (intercontinental ballistic missile) this year, no matter what Trump tweets," he said in an email to CNN.
While US officials and military experts doubt many of Kim's boasts, Trump may very well have to deal with an ICBM test and confront the danger Pyongyang poses to international stability.
Kim declared Sunday that his goal was "to cope against the vicious threats for nuclear war by the Imperialists," a sinister nod to the US and its Asian allies.