The statement described Andersen Air Force Base on Guam as a "beachhead" for a potential USA invasion of North Korea it needed to neutralize.
Trump issued the warning during a briefing on opioid addiction at his golf course in Bedminster, New Jersey. "They will be met with fire and fury like the world has never seen", he said.
"If they had nuclear weapons that can threaten the United States, it's intolerable from the President's perspective".
The president's retweets about his rhetoric Tuesday come as Secretary of State Rex Tillerson was urging calm.
The top USA diplomat has paired that endeavor with an equally important but more subtle project: sending messages of reassurance to China and other Asian nations that the US' aim isn't to destroy North Korea and upend the region, but simply to engage Pyongyang in talks.
A Japanese defence paper and a United States media report said that North Korea may have successfully produced a miniaturised nuclear warhead that can fit inside its missiles.
- They also followed threats by Pyongyang to "make the USA pay dearly" for helping spearhead the passage of new United Nations sanctions against the country in response to two recent missile tests. USA intelligence has also estimated North Korea has enough nuclear material to build dozens of weapons.
However, US Democratic lawmakers criticised Trump for making such a statement.
The US flew two B1B bombers over the Korean peninsula on Monday, according to a spokesman with Pacific Air Forces.
Pyongyang has reacted angrily to the recent deployment of USA strategic bombers over the Korean peninsula. Guam's Homeland Security Advisor George Charfauros told CNN that he remains confident of the island's defenses.
In an annual report, Japan's Defence Ministry on Tuesday concluded that "it is possible that North Korea has achieved the miniaturization of nuclear weapons and has developed nuclear warheads".
On Monday, North Korean officials released a statement through the Korean Central News Agency, a state-run media outlet, in response to the U.N. Security Council's unanimous approval of sanctions on August 5 to penalize the isolated regime for its escalating nuclear and missile programs, including its recent launches of intercontinental ballistic missiles, most recently in late July.
"I take exception to the President's comments because you've got to be sure that you can do what you say you're going to do", the Arizona Republican said in an interview with Phoenix radio station KTAR.
But Democrats slammed Trump for a reaction they charged was "bombastic" and "unhinged".
But it wasn't clear what Trump, who is prone to hyperbole and bombast in far less grave situations, meant by the threat. Dianne Feinstein said in a statement.
"Make no mistake: North Korea is a real threat, but the President's unhinged reaction suggests he might consider using American nuclear weapons in response to a nasty comment from a North Korean despot", Engel said. Aboard his plane as he flew home from Asia, Tillerson insisted the developments didn't suggest the USA was moving closer to a military option to dealing with the crisis.
Threats may be flying between the U.S. and North Korea, but little has changed in the assessment about Pyongyang's military capabilities and the chances of a United States strike.
As for what North Korea's way out looks like, Tillerson replied that the country's leaders in Pyongyang should agree to talks about its nuclear program - and with "the right expectations" of the scope of the discussion.
However, there's debate within the intelligence community that Pyongyang has the required skill and technology.
The Pentagon did not comment on the report, but the Post said the assessment's broad conclusions were verified by two USA officials familiar with the analysis, and CNN said it had confirmed the report. And it marks a stark acceleration from 1994 to 2008, when North Korea did a total of 16 missile tests, Cha said. Asia stocks dipped, with South Korea's benchmark index down 0.9% and Japan's Nikkei 1.6% weaker. "They will be met with fire and fury".
Another was released soon after which broadened the threats leveled against the U.S. mainland.
But Kim is a wily operator and knows what he can get away with, so another missile test or large-scale artillery exercises in North Korea wouldn't be surprising, added Schuster.
In July, military and government reports showed the country's northern border region, which includes the 880 mile (1,415 kilometer) North Korean-Chinese border, was being reinforced with extra Chinese troops. "There's a sense of urgency behind the program that is new to the Kim Jong Un era".
The U.S. now assesses the North Korean arsenal at up to 60 nuclear weapons, more than double most assessments by independent experts, according to the Post's reporting.
North Korea watchers have long maintained that a war between the USA and North Korea is unlikely, largely for two reasons.