"We are totally prepared for the second option. Not a preferred option, but if we take that option, it will be devastating -- I can tell you that -- devastating for North Korea," he said at a White House press conference with Spanish Prime Minister Mariano Rajoy Brey. "That's called the military option. If we have to take it, we will."

Trump has taken a hard-line stance toward Pyongyang's nuclear weapons and ballistic missile programs, saying repeatedly that all options are on the table to deal with the recalcitrant regime.

In an address to the UN General Assembly last week, he vowed to "totally destroy" North Korea if the US was forced to defend itself or its allies. The North Korean leadership has since responded with threats to consider the "highest level" countermeasures, including a hydrogen bomb test over the Pacific Ocean, and accused the American president of declaring war.

"He's acting very badly. He's saying things that should never, ever be said," Trump said in apparent reference to North Korean leader Kim Jong-un. "And we're replying to those things, but it's a reply. It's not an original statement, it's a reply."

Trump added that the North Korea crisis should have been handled by past administrations, but that he'll "fix the mess."

"So we'll see what happens with North Korea," he said.

Trump also called on all "responsible" nations to work together to isolate the "North Korean menace," and thanked Spain and China, in particular, for their respective decisions to expel the North Korean ambassador and cut off banking ties.

US Secretary of State Rex Tillerson is scheduled to travel to Beijing on Thursday to meet with senior Chinese officials.

"Secretary Tillerson will discuss a range of issues, including the President's planned travel to the region, the denuclearization of the Korean Peninsula, and trade and investment," State Department spokeswoman Heather Nauert said in a statement.

"Secretary Tillerson's visit to China reaffirms the Administration's commitment to further broaden and enhance US

economic and security interests in the Asia-Pacific region." (Yonhap)