North Korea launched a ballistic missile on Sunday, Seoul’s military said, just days after a US aircraft carrier arrived for joint exercises with the south in a show of force against Pyongyang.

After talks have long stalled, nuclear-armed North Korea has doubled down on its banned weapons programs and even revised its laws earlier this month to declare itself an “irreversible” nuclear power.

Sunday’s launch is the latest in a record-breaking streak of weapons tests Pyongyang has conducted so far this year, including launching an ICBM at full range for the first time since 2017.

South of the border, hawkish new President Yoon Suk-yeol, who campaigned to crack down on Kim Jong Un, has stepped up joint drills between South Korea and its key security ally, the US.

The Seoul military “detected a short-range missile fired by North Korea around Taechon in North Pyongan province toward the East Sea at 6:53 a.m. today,” the Joint Chiefs of Staff said.

“Our military maintains a full readiness posture and is working closely with the US while increasing surveillance and vigilance,” the statement added.

The Japan Coast Guard issued a warning to ships after the launch, and Tokyo’s Defense Minister Yasukazu Hamada said the missile had reached a maximum altitude of about 50 kilometers (30 miles).

If the missile had a regular trajectory, it likely flew “about 400 kilometers and fell in waters off the east coast of North Korea,” he said, adding that it landed outside of Japan’s exclusive economic zone.

“North Korea’s repeated launches of ballistic missiles are absolutely unforgivable, and the remarkable improvement in its missile technology is something we cannot overlook,” Hamada said.

South Korea’s President Yoon, who took office in May, has promised to step up joint military exercises with the United States after years of failed diplomacy with North Korea under his predecessor.

On Friday, the nuclear-powered USS Ronald Reagan and ships from its strike group docked in the southern port city of Busan, part of a push by Seoul and Washington to operate more strategic US assets in the region.

Yoon will also meet US Vice President Kamala Harris on Thursday when she visits Seoul this week, following a visit by President Joe Biden in May and US House Speaker Nancy Pelosi last month.

“The timing of this latest test falls between the arrival of the USS Ronald Reagan this week and VP Harris’ visit to Seoul next week,” Soo Kim, an analyst at RAND Corporation, told AFP.

“This is North Korea’s way of defying the alliance and injecting itself at an opportune time.”

The USS Reagan will participate in joint exercises off the east coast of South Korea this month.

Washington is Seoul’s main security ally, stationing about 28,500 troops in South Korea to protect it from the North.

The two countries have long held joint drills that they claim are purely defensive, but North Korea sees them as rehearsals for an invasion.

“Pyongyang could make a show of force while a US aircraft carrier visits South Korea for defense drills,” said Leif-Eric Easley, a professor at Ewha University in Seoul.

“But North Korea’s major tests are, above all, part of a long-term campaign to further develop offensive military capabilities.”

South Korean and US officials have been warning for months that North Korean leader Kim Jong Un is preparing for another nuclear test.

South Korea had also spotted signs the North was preparing to launch a submarine-launched ballistic missile (SLBM), the president’s office said Saturday, a weapon Pyongyang last tested in May.

The isolated regime has tested nuclear weapons six times since 2006. The latest and most powerful, in 2017 – which Pyongyang dubbed a hydrogen bomb – had an estimated yield of 250 kilotons.

“North Korea may postpone its seventh nuclear test out of respect for China’s upcoming political conference, which Xi Jinping is firmly scripting to expand its leadership,” Easley said.

“But Pyongyang’s self-control has its limits.”