President Donald Trump on Tuesday warned North Korea about facing “fire and fury” if the isolated nation makes more threats against the United States.

“North Korea best not make any more threats to the United States,” Trump told reporters, speaking slowly and deliberately with his arms crossed in front of him. “They will be met with fire and fury like the world has never seen. He has been very threatening … and as I said they will be met with fire, fury and frankly power, the likes of which this world has never seen before.”

Later Tuesday, North Korea’s state media said that the country was considering a strategy to strike the U.S. Pacific territory of Guam with mid- to long-range missiles, according to Reuters.

A spokesman for the Korean People’s Army, in a statement carried by North Korea’s state-run KCNA news agency, said the strike plan will be “put into practice in a multi-current and consecutive way any moment” once leader Kim Jong Un makes a decision.

Trump made his remarks while getting briefed on the U.S. opioid epidemic during what he calls a “working vacation” at his New Jersey golf club.

His comments came hours after revelations that Pyongyang has successfully created a miniaturized nuclear weapon designed to fit inside its missiles. While miniaturizing marks a major step in North Korea’s nuclear ambitions, it does not necessarily mean the country has an accurate nuclear-equipped intercontinental ballistic missile, yet.

The development raises the stakes for Trump and other world leaders, who already faced difficult and limited options in dealing with North Korea’s aggression. Trump has tried to leverage China, Pyongyang’s only major ally, to get North Korea to change its behavior, but he has lamented a lack of success with Beijing.

National security advisor H.R. McMaster recently said Trump is “not going to tolerate North Korea being able to threaten the United States.”

Pyongyang has repeatedly vowed retribution against the U.S. following sanctions or other measures meant to deter its nuclear and missile programs. After the U.N. imposed the newest sanctions, North Korea said it would bring “thousands-fold” revenge against the U.S. Full Report