North Korea recently used what would be its largest ever intercontinental ballistic missile (ICBM) system in two secretive launches, likely paving the way for a resumption of long-range tests, US and South Korean officials said.
North Korea froze its ICBM and nuclear tests in 2017 after launching its first missiles capable of reaching the United States. It has also not tested a nuclear weapon since then but leader Kim Jong Un has warned of a return to testing both.
The escalation in North Korea tensions comes as South Korea on Wednesday elected a new conservative president.
Yoon Suk-yeol has said preemptive strikes may be needed to counter any imminent attack by the North and has vowed to buy American THAAD missile interceptors, while remaining open to restarting stalled denuclearisation talks.
In launches on Feb. 27 and March 5, North Korea did not specify what missile was used, but said they tested components for reconnaissance satellites Kim said would soon be launched to monitor military activity by the United States and its allies.
"The purpose of these tests, which did not demonstrate ICBM range, was likely to evaluate this new system before conducting a test at full range in the future, potentially disguised as a space launch," Pentagon spokesman John Kirby said in a statement.
The US Treasury, which has imposed a range of sanctions on North Korea over its weapons programmes, will announce new actions on Friday to help prevent North Korea "accessing foreign items and technology that enable it to advance its weapons programmes," a senior US administration official told reporters in Washington, speaking on condition of anonymity.
These steps would be followed by a range of further actions in coming days, the official added, without giving any details of the measures.
Japanese Prime Minister Fumio Kishida and Yoon said they had agreed to ramp up three-way ties with the United States in responding to North Korea's evolving military threat.
Japan is also considering imposing additional sanctions against North Korea, as well as other diplomatic options, Kishida told reporters after a phone call with the South Korean president-elect.
Rockets and Satellites
The United States and South Korea both said the missile system, known as the Hwasong-17, was unveiled at an October 2020 military parade in Pyongyang and reappeared at a defence exhibition in October 2021.
The Hwasong-17 would be North Korea's longest-range weapon, carried on a transporter vehicle with 11 axles, with some analysts calling it a "monster."
Analysts said the tests likely only used only one stage of the Hwasong-17, and may have adjusted its fuel use to fly at lower altitudes.
Washington called the ICBM tests a "serious escalation requiring a united global response". Seoul issued strong condemnation and urged Pyongyang to immediately stop actions that heighten tension.
The intelligence assessments, released simultaneously by the United States and South Korea, came as North Korean state media reported Kim had inspected the Sohae Satellite Launching Ground.
The facility has been used to put a satellite in orbit and also to test various missile components including rocket engines and space launch vehicles that South Korean and US officials say require similar technology to that used in ICBMs.
North Korea "has historically used its space launches to try to hide its attempted advancements of its ICBM programme", the US official told reporters.
At the Sohae station, Kim inspected facilities and ordered modernising and expanding it to ensure that "various rockets could be launched to carry multi-purpose satellites, including a military reconnaissance satellite," the North's KCNA news agency reported.
"I think that the North Koreans are genuinely working on a set of technologies that have applications across both ICBMs and satellites," said Ankit Panda, a senior fellow at the US-based Carnegie Endowment for International Peace.
South Korea's unification ministry, which handles inter-Korean affairs, said it was monitoring Kim's movements and urged North Korea to refrain from further stoking tension.