NEW YORK • North Korean leader Kim Jong Un oversaw a live-fire military exercise that potentially included the country's first ballistic missile launch since 2017 - challenging United States President Donald Trump's bottom line in nuclear talks.

Mr Kim watched as "large-calibre, long-range multiple-rocket launchers and tactical guided weapons" were fired off North Korea's eastern coast last Saturday, according to the official Korean Central News Agency (KCNA). The state media report yesterday was accompanied by a photo of what non-proliferation analysts said appeared to be the launch of a short-range ballistic missile.

Although such a test would violate United Nations resolutions imposing sanctions on North Korea, it would stop short of breaching Mr Kim's pledge to refrain from testing longer-range missiles that could threaten the US. Mr Trump had earlier brushed off the incident, saying in a tweet that Mr Kim "does not want to break his promise to me".

Dr Vipin Narang, associate professor of political science at the Massachusetts Institute of Technology, said: "Kim Jong Un may be starting his 'push-the-line' strategy, gradually seeing how much Trump will turn a blind eye to. Not good."

Neither the US nor South Korean authorities immediately confirmed a ballistic missile launch, which was bolstered by a satellite image from Planet Labs showing what appeared to be a single missile contrail at the exercise site.

South Korea's Defence Ministry said yesterday that the North tested "new tactical weapons" and artillery that travelled 70km to 240km, without mentioning "missiles". Mr Nathan Hunt, an independent defence researcher, said the South Korean statement was "skirting over" the North's ballistic missile launch. "They did indeed test a new short-range missile or, as others call it, close-range ballistic missile, and this was not just an artillery drill."

Either way, the exercise was Mr Kim's most significant provocation since he launched an intercontinental ballistic missile in November 2017, declared his nuclear weapons programme "complete" and opened talks. Mr Kim has expressed increasing frustration since Mr Trump refused his demands for sanctions relief and walked out of their second summit in Hanoi in February.

Analysts said the weapon featured in the KCNA photograph appeared to be a solid-fuel ballistic missile similar to a Russian Iskander that could be stored while fuelled, deployed and fired with less detection time. North Korea had put a similar weapon on display during a military parade in February last year.

"This is problematic in that, despite it being short-range, it's still a ballistic missile - and it violates the sanctions resolutions," said Dr Kim Dong-yub, professor of North Korea studies at Kyungnam University's Institute of Far Eastern Studies in South Korea.

The North Korean exercise came days ahead of US Special Representative Stephen Biegun's expected arrival in the region. The top American nuclear envoy is scheduled to travel to Tokyo tomorrow and to Seoul on Thursday.

Adding to the confusion were South Korea's revisions of its accounts of the nature of the weapons discharged from North Korea's eastern port of Wonsan. After first calling them "missiles", the South Korean Joint Chiefs of Staff changed the description to "projectiles".

North Korean media reports on the latest exercise included no references to the US or South Korea. That was possibly part of an effort to limit damage to last September's agreement with Seoul, said Federation of American Scientists adjunct senior fellow Ankit Panda. "They emphasised technological sophistication and framed the exercise in fairly defensive terms," he said.

BLOOMBERG