U.S. President Donald Trump is warning North Korea to expect "big, big trouble" if it acts against Guam.

Speaking at his golf resort in New Jersey on Friday, he promised the American territory would be "very safe."

Trump also told reporters that he hopes North Korea will fully understand the gravity of what he said, and what he said is what he means, and that those words are very easy to understand.

He added that if Kim Jong-un utters one threat in the form of an overt threat with respect to Guam or anyplace else that's an American territory or an American ally, he will truly regret it and he will regret it fast.

Earlier on Friday, Trump said the U.S. military was "locked and loaded" to deal with North Korea, should the need arise.

He tweeted that "military solutions are now fully in place, locked and loaded, should North Korea act unwisely" and that "hopefully Kim Jong-un will find another path." 

Earlier in the week, the president threatened to rain "fire and fury" on Pyongyang and has been stepping up warnings against the regime. 

But Trump refused to comment on news reports that U.S. Special Representative for North Korea Policy Joseph Yun has engaged in back channel diplomacy with North Korea for months.