The US President says that millions of Americans support him because he is “sticking up for our nation” against North Korea.
Donald Trump has said that North Korean leader Kim Jong Un will “truly regret” any action he takes against the US territory of Guam.
The President told reporters: “I hope that they are going to fully understand the gravity of what I said, and what I said is what I mean.
“If he does anything 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.”
Mr Trump was speaking at his Bedminster golf resort in New Jersey, where he is on holiday.
Hours earlier, the President tweeted that military solutions were “locked and loaded” should North Korea “act unwisely”.
Mr Trump dismissed critics as attacking his words only “because it’s me”, adding that his rhetoric would be welcomed as “a great statement” if “somebody else” had said it.
He said that millions of Americans supported him because “finally we have a president that’s sticking up for our nation and frankly sticking up for our friends and our allies”.
But German Chancellor Angela Merkel urged both sides to tone down their tough talk.
She said: “I don’t see a military solution and I don’t think it’s called for.
“I think escalating the rhetoric is the wrong answer.”
Mr Trump responded by saying: “Let her speak for Germany. She’s certainly not referring to the United States.”
China, North Korea’s main diplomatic ally, called on both parties to be “cautious with their words and actions, and contribute more toward easing tensions and enhancing mutual trust”.
President Xi Jinping spoke to Mr Trump by phone, calling on the “relevant side” to exercise restraint, according to Chinese state television.
Mr Xi said it was in the interests of China and the US to maintain peace on the Korean peninsula and to achieve its denuclearisation.
:: Propaganda and sightseeing at the Korean border
Russia’s foreign minister Sergei Lavrov said Moscow is deeply concerned about the developments, estimating that the risk of a military conflict is “very high”.
Mr Lavrov added that “when it comes close to a fight, the one who is stronger and wiser should be the first to step back from the brink”.
North Korea’s official KCNA news service said in an editorial that Mr Trump was “driving the situation on the Korean peninsula to the brink of a nuclear war”, describing the US as a “heinous nuclear war fanatic”.
The latest words come after nearly a week of threats exchanged between the US and North Korea, with the latter vowing to send missiles flying over western Japan to land near the US Pacific territory of Guam.
This came after Mr Trump promised North Korea “fire and fury like the world has never seen” if it provoked the US.
Japan earlier began deploying land-based Patriot interceptors at four cities, while American and South Korean officials said they planned to go ahead with military exercises later this month, which North Korea has described as a rehearsal for war.