Pyongyang said it was considering a plan to fire medium-to-long-range rockets at Guam according to the North Korean state news agency. And on Tuesday President Donald Trump issued an apocalyptic warning to North Korea, saying it faced "fire and fury" over its weapons programs.
Trump's comments marked a sharp intensification of Washington's rhetoric over the North's nuclear and missile programs, which saw a seventh set of United Nations sanctions imposed on it at the weekend.
The remarks also appeared to echo Pyongyang's own regular threats, most recently repeated on Monday, to turn Seoul, South Korea into a "sea of flames."
"North Korea best not make any more threats to the United States," said Trump, speaking from his golf club in New Jersey. "They will be met with fire and fury like the world has never seen."
Trump's tone was markedly different to Secretary of State Rex Tillerson's assurances last week that Washington was not seeking regime change in Pyongyang.
North Korea raised the stakes just hours later, saying it was considering missile strikes near US strategic military installations on the Pacific island of Guam.
Once finalized, the plan could be put into action at "any moment" once leader Kim Jong-un made a decision, the official Korean Central News Agency (KCNA) quoted a military statement as saying.
The remote island of Guam — a 210-square-mile dot in the Pacific — is a key US military outpost and home to some 6,000 US troops spread across facilities including the sprawling Anderson Air Force Base, as well as Naval Base Guam.
Guam-based US B1-B bombers overflew the Korean peninsula on Tuesday, which KCNA said "proves that the US imperialists are nuclear war maniacs."
Earlier, the Washington Post quoted a Defense Intelligence Agency analysis as saying officials think North Korea now has "nuclear weapons for ballistic missile delivery" — including in its intercontinental ballistic missiles (ICBMs) — making it a potent threat against neighbors and possibly the United States.
The Pentagon did not comment on the story, but the Post said two US officials familiar with the analysis had verified the assessment's broad conclusions, and CNN said it had confirmed the report.
Experts have long differed over the North's exact capabilities, and a similar DIA assessement four years ago was dismissed by other intelligence organizations.
But all agree it has made rapid progress under leader Kim Jong-un.
Last month Pyongyang carried out its first two successful ICBM launches, the first — described by Kim as a gift to "American bastards" — showing it could reach Alaska, and the second extending its range even further, with some experts suggesting New York could be vulnerable.
Trump said Kim "has been very threatening beyond a normal state."
"As I said, they will be met with the fire and fury and, frankly, power," he told reporters.
US officials have repeatedly said this year that military action against the North was an "option on the table."
But analysts and politicians reacted to the US president's latest remarks with derision.
"Trying to out-threaten North Korea is like trying to out-pray the Pope," John Delury of Seoul's Yonsei University said on Twitter.
Security commentator Ankit Panda added: "Trump's comments were dangerous and unusual; North Korea's threat was also specific, but not unusual."
Wilson Center fellow and former AP Pyongyang bureau chief Jean Lee said that war is a possibility but she considers "a lot of this to be rhetoric."
What really concerns her, she said, is that a mishap or miscalculation could force troops in the area to take military action. "We've seen in the past that some of these tensions tipped over into conflict. I was here in 2010 when a miscommunication between North Korea and South Korea ended in an artillery exchange on a Korean frontline island and civilians were killed."
Congressman Eliot Engel, the Democratic senior member of the House Committee on Foreign Affairs, chastised Trump for drawing an "absurd" red line that Kim would inevitably cross.
"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 in a statement.
Deputy Secretary of State John Sullivan said Washington continues to work to make sure China and other countries enforced the new UN sanctions.
On Guam, Governor Eddie Calvo downplayed Pyongyang's statement, saying that "currently there is no threat" and the territory was "prepared for any eventuality."
Dana Williams, the executive editor of the Pacific Daily News in Guam, said the island's residents found Calvo's speech reassuring.
"After all," she said, "this is not the first time Guam has been threatened by North Korea. I remember in the '90s, they were talking about developing a missile that could hit Guam with a nuclear warhead. Of course then it was some time in the distant future. As the years have gone on, we have watched the technology develop."
The Post also reported that another intelligence assessment estimated North Korea now has up to 60 nuclear weapons, more than previously thought.
Despite the advance, North Korea still must overcome technical hurdles before it will be seen to have perfected the technology.
After Kim's second ICBM test, experts said it appeared the "re-entry vehicle" that would carry a warhead back into Earth's atmosphere from space had failed in the intense heat.
Former Los Alamos National Laboratory director Siegfried Hecker told the Bulletin of the Atomic Scientists he did not think North Korea yet had sufficient missile or nuclear test experience "to field a nuclear warhead that is sufficiently small, light and robust to survive an ICBM delivery."
North Korea has vowed that the new UN sanctions would not stop it from developing its nuclear arsenal, and that it would never negotiate it away.