North Korea says it will take "prompt corresponding actions" if the United States resorts to military force, state media reports, as tensions rise ahead of Pyongyang's year-end deadline for stalled denuclearisation talks.
The statement came on Wednesday just hours after North Korea announced it would convene a rare gathering of top ruling-party officials later this month, and state media showed photos of leader Kim Jong-un taking a second symbolic horse ride on the country's sacred Mt Paektu.
US President Donald Trump, in Britain for a NATO summit, said on Tuesday that Washington could use military force against North Korea "if we have to", though he added he still hoped for talks.
Kim was "displeased to hear" those comments, Pak Jong-chon, chief of the General Staff of the Korean People's Army, said in a statement carried by North Korea's state news agency KCNA.
"I clearly state here that if the US uses any armed forces against the DPRK, we will also take prompt corresponding actions at any level," Pak said, using the initials of North Korea's official name, the Democratic People's Republic of Korea.
"The use of armed forces against the DPRK will be a horrible thing for the US."
North Korea and the US are still technically at war and the state of truce could turn into an "all-out armed conflict any moment" even by accident, Pak said.
For the second time in two months, Kim visited Mt Paektu on horseback, this time accompanied by senior military officers, aimed at instilling the mountain's "indefatigable revolutionary spirit" in the people, KCNA reported.
Kim has warned the US it has until the end of the year to offer more concessions or North Korea will pursue an unspecified "new path". Analysts say that may include a resumption of intercontinental ballistic missile launches or nuclear tests.
US officials have called for more talks while playing down the deadline as "artificial" and warning that it would be a "huge mistake and a missed opportunity" for North Korea to take any provocative steps.
But North Korean state media have carried a steady chorus of statements in recent weeks, saying Washington should not ignore the warning and dismissing US calls for talks as a stalling tactic.
The 15-member United Nations Security Council met behind closed doors on Wednesday over missile launches conducted by North Korea last week. Following the meeting, the council's five European members condemned Pyongyang's "provocative actions".
"The DPRK has conducted 13 sets of ballistic missile launches since May and continued to operate its nuclear program", Britain, France, Poland, Belgium and Germany said in a statement, urging Pyongyang to engage in meaningful talks with the US on denuclearisation.
North Korea announced that a Plenary Meeting of the Central Committee of the ruling Workers' Party of Korea would meet sometime in late December.
KCNA said the plenum would discuss and decide on "crucial issues" in light of the "changed situation at home and abroad".
The timing of this plenum is unusual because it comes before the year-end deadline, as well as before Kim's expected New Year's address, said Rachel Minyoung Lee, an analyst with NK News, a website that monitors North Korea.
"That Pyongyang is opting to hold this meeting before the end of the year indicates its strong resolve," she said. "Taking the party plenum announcement and the Mount Paektu visit together, the 'resolve' seems to be that North Korea will not cave in to the US, and that it will keep charging on despite the difficulties."
Australian Associated Press