Donald Trump promised that North Korea will not develop a “nuclear weapon capable of reaching parts of the U.S.” in a stern Twitter warning issued Monday evening.

“North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the U.S. It won’t happen!” the president-elect declared in a tweet.

The message comes the day after the North Korean dictator promised to develop capacity for the most powerful weapon on the planet to reach the US.

Kim Jong Un made the brash declaration that his nation was close to developing an intercontinental ballistic missile in a televised New Year’s Day address.

“Research and development of cutting edge arms equipment is actively progressing and ICBM rocket test launch preparation is in its last stage,” he declared.