Seoul, South Korea - North Korea said Friday it flight-tested a solid-fuel intercontinental ballistic missile for the first time, a possible breakthrough in its efforts to acquire a more powerful, harder-to-detect weapon targeting the continental United States.

North Korea's official Korean Central News Agency issued the report a day after the country's neighbors detected a launch of a long-range missile from near Pyongyang, which extended a run of weapons displays involving more than 100 missiles fired into the sea since the start of 2022.

Later Friday, the U.S. flew nuclear-capable B-52 bombers to the Korean Peninsula for joint aerial training with South Korean warplanes in their latest show of force against North Korea. The exercise was aimed at sharpening combined operational abilities and demonstrating the credibility of U.S. commitment to leverage its full military capabilities, including nuclear, to defend South Korea, according to Seoul's Defense Ministry.

North Korea's Thursday's test didn't appear to demonstrate the weapon's full capacity, and it remains unclear how far North Korea has come in mastering technologies to ensure the warhead would withstand atmospheric reentry and accurately strike targets. Still, analysts said the test was likely a meaningful advance in North Korea's goal of building a nuclear arsenal that could directly threaten the United States.

KCNA said the launch was supervised on site by North Korean leader Kim Jong Un, who described the missile - named Hwasong-18 - as the most powerful weapon of his nuclear forces that would enhance counterattack abilities in the face of external threats created by the military activities of the United States and its regional allies.

Kim pledged to further expand his nuclear arsenal and warned the test would make North Korea's enemies "experience a clearer security crisis, and constantly strike extreme uneasiness and horror into them by taking fatal and offensive counter-actions until they abandon their senseless thinking and reckless acts."

North Korea has justified its weapons demonstrations as a response to the expanding military exercises between the United States and South Korea, which the North condemns as invasion rehearsals while using them as a pretext to push further its own weapons development.

Kim added that the Hwasong-18 would rapidly advance North Korea's nuclear response posture and further support an aggressive military strategy that vows to maintain "frontal confrontation" against its rivals.

North Korea has tested various intercontinental missiles since 2017 that demonstrated the potential range to reach the U.S. mainland, but the others use liquid fuel that must be added relatively close to the launch and they cannot remain fueled for prolonged periods.

An ICBM with built-in solid propellants would be easier to move and hide and fired quickly, reducing the opportunities for opponents to detect and counter the launch. It's not immediately clear how close the North is to having a functional solid-fuel ICBM capable of striking the U.S. mainland.

South Korea's Defense Ministry in a statement described Hwasong-18's flight as a "mid-phase test" and said North Korea would need more time and effort to complete the system. It maintains that North Korea's technologies haven't reached the point where it can protect its ICBM warheads from the harsh conditions of atmospheric reentry.

Last month, South Korean Defense Minister Lee Jong-Sup also told lawmakers that North Korea likely hasn't yet acquired the technology to place nuclear warheads on its newer short-range missiles targeting South Korea, though he acknowledged the country was making considerable progress on it.

Still, Thursday's test marked a "significant breakthrough for the North Koreans, but not an unexpected one," said Ankit Panda, an expert with the Carnegie Endowment for International Peace.

"The primary significance of solid-fuel ICBMs is in terms of what they'll do for the survivability of North Korea's overall ICBM force," he said.

"Because these missiles are fueled at the time of manufacture and are thus ready to use as needed, they will be much more rapidly useable in a crisis or conflict, depriving South Korea and the United States of valuable time that could be useful to preemptively hunt and destroy such missiles."

North Korean state media published photos of the missile blasting off from a launch vehicle at a test site inside a forest as Kim watched from an observation post along with military officials and his daughter.

KCNA described the Hwasong-18 as a three-stage missile with the first stage tested at a standard ballistic trajectory and the others programmed to fly at higher angles after separation to avoid North Korea's neighbors. It wasn't immediately clear how the third stage was tested or where the warhead would theoretically be placed.

The agency said the first and second stages fell into waters off the country's eastern coast. The official Rodong Sinmun newspaper published an aerial photo of an object it described as the third stage following separation, but state media provided no further details.

Kim Dong-yub, a professor at the University of North Korean Studies in Seoul, said North Korea for the test likely designed the third stage as an empty device and simply let it fall after separation.

He noted that North Korea didn't release details about how high the missile went, which suggests it wasn't tested at the weapon's full capacity and range, and said the North likely will test the system several more times.

Soo Kim, an expert with Virginia-based consultancy LMI and a former CIA analyst, said each successive test by North Korea "seems to demonstrate greater options for the regime to provoke and threaten the region."

"With the Day of the Sun festivities coming up, and a U.S.-South Korean summit around the corner, the timing is also ripe for a North Korean provocation for (Kim Jong Un) to yet again remind us that his weapons are getting bigger, better, and all the more challenging for the U.S., South Korea, and the international community to deal with," she said.

She was referring to the birth anniversary of Kim's state-founding grandfather, Kim Il Sung, which falls on Saturday, and a planned summit in Washington this month between President Joe Biden and South Korean President Yoon Suk Yeol.

Solid-fuel ICBMs highlighted an extensive wish list Kim announced under a five-year arms development plan in 2021, which also included tactical nuclear weapons, hypersonic missiles, nuclear-powered submarines and spy satellites.

The North has fired around 30 missiles this year alone over 12 different launch events as both the pace of its weapons development and the U.S.-South Korean military exercises increase in a cycle of tit-for-tat. The U.S. and South Korean militaries conducted their biggest field exercises in years last month and separately held joint naval and air force drills involving a U.S. aircraft carrier strike group and nuclear-capable U.S. bombers.

North Korea claimed the drills simulated an all-out war against North Korea and communicated threats against it. The United States and South Korea have said their exercises are defensive in nature and expanding them was necessary to cope with the North's evolving threats.

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