TOKYO — The two Koreas test-fired ballistic missiles hours apart on Wednesday in the latest sign of the intensifying arms race on the peninsula amid stalled diplomatic efforts.

North Korea fired two short-range ballistic missiles off its east coast, just two days after it announced a test of a new long-range cruise missile capable of hitting Japan — a move that's likely in violation of U.N. Security Council resolutions and puts renewed pressure on the Biden administration's efforts to end North Korea's nuclear and ballistic missile program.

South Korea then conducted its own test hours later, launching an underwater ballistic missile from a submarine and successfully hitting a designated target — making it one of just a handful of countries with the capability to do so.

On Sept. 13, North Korea said it tested a cruise missile followed by two ballistic missiles tests. Hours later, South Korea tested its own ballistic missile. (The Washington Post)

While their timing may be coincidental, the two tests point to growing tensions on the Korean Peninsula. Pyongyang is retreating further from engaging with other countries during a self-imposed coronavirus lockdown, and Seoul is seeking to reduce its military dependence on the United States.

“It’s sort of a competition of neighbors, like keeping up with the Joneses, to some extent,” said Kazuto Suzuki, a senior research fellow at the Asia Pacific Initiative in Tokyo and former member of the Panel of Experts that assists the U.N. Security Council’s Iran Sanctions Committee.

North Korea’s projectiles were identified as short-range ballistic missiles by the South Korean Joint Chiefs of Staff. It was the first such test since March.

The back-to-back weapons tests by North Korea both complicate matters for Japanese officials and increase “the vulnerability of American forces in Japan,” Suzuki said.

“It complicates the defense planning for Japan and probably for Americans,” he said. “The combination of capabilities . . . makes it much harder for defending Japan from North Korean missiles.”

Meanwhile, nuclear talks have been deadlocked since 2019, when negotiations fell through during a U.S.-North Korea summit in Vietnam. North Korea so far has not responded to outreach efforts by the Biden administration, which has not signaled any intention to offer the sanctions relief Pyongyang has demanded.

In a statement, a spokeswoman for the State Department said the United States condemns North Korea’s ballistic missile launch and reiterated its commitment to defending South Korea and Japan.

“This launch is in violation of multiple UN Security Council Resolutions and poses a threat to the DPRK’s neighbors and other members of the international community. We remain committed to a diplomatic approach to the DPRK and call on them to engage in dialogue,” the statement read, referring to North Korea by its official name, the Democratic People’s Republic of Korea.

U.S. military officials said they have assessed that Wednesday’s launch “does not pose an immediate threat to U.S. personnel or territory, or to our allies.” Still, “the missile launch highlights the destabilizing impact of the DPRK’s illicit weapons program,” the U.S. Indo-Pacific Command said in a statement.

A series of senior-level talks are taking place this week as officials in South Korea, Japan, China and the United States discuss how to re-engage Pyongyang in nuclear talks.

President Biden’s nuclear envoy, Sung Kim, is in Tokyo this week to meet with Japanese and South Korean officials. Meanwhile, Chinese Foreign Minister Wang Yi is in Seoul for meetings with his South Korean counterparts regarding the stalled nuclear diplomacy with the North.

On Monday, South Korean President Moon Jae-in was briefed on a host of other new weapons under development, including a supersonic cruise missile, and a successful test of a new long-range air-to-surface missile to be used on a new fighter jet, the KF-21 Boramae.

Moon has been increasing the country’s defense spending in an effort to decrease its military dependence on the United States. Earlier this year, the United States lifted restrictions on South Korea’s ability to develop missiles, under an agreement reached during Moon’s summit with Biden in Washington.

“The increase in our missile power can be a sure deterrent against North Korean provocations,” Moon said in a statement Wednesday.

In a statement released through state media, Kim Yo Jong, the powerful sister of North Korea’s leader, pushed back against Moon’s use of the word “provocation” and warned that such language would jeopardize any improvements in inter-Korean relations. She said in her statement that Pyongyang is following its scheduled plans for self-defense military capabilities.

The development in South Korea gives the country “a more survivable retaliatory strike capability” against the North that Pyongyang would need to consider, said Daniel Pinkston, an international relations professor at Troy University in Seoul and nonproliferation policy expert.

South Koreans have displayed technical advantages in their ability to have greater “command and control” over their systems than the North, he said.

Even though the South Korean system does not have nuclear weapons capability, “it’s difficult for North Korea to defend against,” he said.

North Korea’s tests this week are consistent with the country’s announced schedule for enhancing its military capabilities for deterrence, said Kim Joon-hyung, an international relations professor at South Korea’s Handong Global University and former foreign policy adviser to Moon.

“Pyongyang is doing what they planned in the context of enhancing its military capabilities for deterrence,” he said. “They are doing this also for domestic purpose. This is what Pyongyang does the best anyway, especially under the dire economic and pandemic crisis situation.”

The Japanese coast guard said the projectiles landed outside the exclusive economic zone, meaning they did not reach Japanese territory.

Japanese Prime Minister Yoshihide Suga condemned the missile launches on Wednesday and said that the tests are “threatening the peace and security of our country and region. They’re also violating the U.N. Security Council resolutions.”

Japan’s Defense Ministry said that “North Korea’s recent repeated launches of ballistic missiles and other projectiles are a serious problem for Japan and the international community as a whole,” Kyodo News reported.

The U.N. Security Council took no action in response to North Korea’s launch of two ballistic missiles in March.