North Korea dismissed as a "load of nonsense" warnings by U.S. President Donald Trump that it would face "fire and fury" if it threatened the United States, and outlined on Thursday detailed plans for a missile strike near the Pacific territory of Guam.
North Korea's apparently rapid progress in developing nuclear weapons and missiles capable of reaching the U.S. mainland has fueled tensions that erupted into a war of words between Washington and Pyongyang this week, unnerving regional powers and global investors.
Trump's unexpected remarks prompted North Korea to say on Thursday it was finalizing plans to fire four intermediate-range missiles over Japan to land 30-40 km (18-25 miles) from Guam, adding detail to a plan first announced on Wednesday.
Guam, more than 3,000 km (2,000 miles) to the southeast of North Korea, is home to about 163,000 people and a U.S. Navy base that includes a submarine squadron and a Coast Guard group, and an air base.
"Sound dialogue is not possible with such a guy bereft of reason and only absolute force can work on him," a report by the North's state-run KCNA news agency said of Trump.
The army will complete its plans in mid-August, ready for North Korean leader Kim Jong Un's order, KCNA reported, citing General Kim Rak Gyom, commander of the Strategic Force of the Korean People's Army.
While North Korea regularly threatens to destroy the United States and its allies, the report was unusual in its detail.
Masao Okonogi, professor emeritus at Japan's Keio University, said before the latest KCNA report that Pyongyang may be issuing a warning or advance notice of changes to its missile testing program rather than threatening an attack.
"I believe this is a message saying they plan to move missile tests from the Sea of Japan to areas around Guam," he told Reuters. "By making this advance notice, they are also sending a tacit message that what they are going to do is not a actual attack."
Experts said the detail provided by North Korea made it likely it would follow through with its plans to avoid being seen as weak or lacking in resolve.
Guam Governor Eddie Calvo said there was no heightened threat from North Korea.
"They like to be unpredictable, they'll pop a missile off when no one is ready and they've done it quite a few times," he told Reuters in an interview.
"They're now telegraphing their punch, which means they don't want to have any misunderstandings. I think that's a position of fear," he said.
Lee Choon-geun, senior research fellow at South Korea’s state-run Science and Technology Policy Institute, said there was a risk that any missile could land much closer to Guam than planned.
"The United States will consider it an apparent attack if it lands within its territorial waters and, given the risks involved, will most likely try to shoot them down before they land anywhere close to Guam and its territorial sea," Lee told Reuters.
"This could elevate the threats to an unprecedented level."
The U.S. Seventh Fleet currently has six Aegis ballistic missile defense ships in the region capable of targeting North Korean missiles, and Japan has a further four. Guam also has a Terminal High Altitude Area Defense (THAAD) anti-missile system, similar to the that recently installed in South Korea.
Japan could legally intercept a North Korean missile headed toward Guam, its defense minister said on Thursday, but experts believe Japan does not currently have the capability to do so.
The United States and South Korea remain technically still at war with North Korea after the 1950-53 Korean conflict ended with a truce, not a peace treaty.
Tension in the region has risen since North Korea carried out two nuclear bomb tests last year and two intercontinental ballistic missile tests in July. Trump has said he will not allow Pyongyang to develop a nuclear weapon capable of hitting the United States.
U.S. Defense Secretary Jim Mattis issued a stark warning on Wednesday, telling Pyongyang it would lose any arms race or conflict.
"The DPRK should cease any consideration of actions that would lead to the end of its regime and the destruction of its people," Mattis said in a statement, using the acronym for North Korea's official name, the Democratic People's Republic of Korea.
Washington has warned it is ready to use force if needed to stop North Korea's ballistic missile and nuclear programs but that it prefers global diplomatic action. The U.N. Security Council unanimously imposed new sanctions on North Korea on Saturday.
In a video of a rally in Pyongyang released by KCNA, Pak Hyong Ryol, the manager of a Pyongyang cornstarch factory, said North Koreans did not mind any kind of sanctions.
"They cannot stop our advance. This is the answer of our heroic Kim Il Sung-Kim Jong Il working class which has been grown up under the warm care of the Party,” Pak said, referring to North Korea's first two leaders.
North Korea accuses Washington of devising a "preventive war" and has said any plans to execute this would be met with an "all-out war, wiping out all the strongholds of enemies, including the U.S. mainland".
China, North Korea's main ally, has consistently urged both sides to work to lower tensions.
Influential Chinese state-run tabloid the Global Times said the North Korean nuclear issue was heading toward confrontation and it was time for the United States to respond to Pyongyang's security concerns.
"North Korea has almost been completely isolated by the outside world. Under such extreme circumstances, Pyongyang will weigh all its possible options," it said in an editorial on its website on Thursday. "Washington should stimulate Pyongyang's desire to engage with the outside world and return to the international community."