North Korea test-fired what is believed to be a ballistic missile built to be launched from a submarine from waters off its east coast into Japan’s exclusive economic zone off Shimane Prefecture on Wednesday, showing off military technologies that if successfully developed would make it significantly more difficult for the United States to destroy its nuclear arsenal.

The test-firing, which was immediately detected by Tokyo and Seoul, was carried out just hours after Pyongyang said it would resume stalled denuclearization talks with Washington.

North Korea apparently demonstrated its missile technologies with the aim of gaining bargaining power against the United States during the upcoming denuclearization talks.

Japanese defense officials said North Korea probably still owns only outdated submarines that are unable to go far into the Pacific Ocean and directly attack the U.S. mainland.

Still, the test-firing represents significant progress in Pyongyang’s missile program and a North Korean SLBM-capable submarine would increase the survivability of its nuclear arsenal, experts say.

“The firing of this missile poses a grave threat to the security of our country,” Defense Minister Taro Kono told reporters after the launch.

“North Korea has been enhancing missile-related technologies and promoting nuclear and missile development programs. We can never overlook a firing like this, which is also a grave problem for international society as well,” Kono said.

U.S. President Donald Trump has been eager to resume denuclearization talks with the North, apparently trying to secure diplomatic achievements ahead of next year’s presidential election.

To resume talks, Trump has sometimes shown apparent willingness to appease Pyongyang, saying he doesn’t care much about Pyongyang’s test-firing of short-range ballistic missiles — many of which are capable of directly hitting Japan.

Facing reporters on Wednesday, both Chief Cabinet Secretary Yoshihide Suga and Kono emphasized that Wednesday’s test-firing violates resolutions of the United Nations Security Council, which ban any firing of ballistic missiles by North Korea.

Suga pointed out that Wednesday’s ballistic missile launch by North Korea was the first to be fired into Japan’s EEZ since November 2017.

According to South Korea’s military, the projectile was believed to be a model of the Pukguksong ballistic missile. Said by the military to possibly be the first part of a two-stage rocket, the missile was fired from off the east coast near Wonsan in an easterly direction at 7:11 a.m.

Kono said that the missile landed in Japan’s EEZ about 350 kilometers north of Dogo Island, Shimane Prefecture, at around 7:27 a.m. after flying 450 km at an altitude of up to 900 km.

Earlier, the Defense Ministry had said North Korea fired two projectiles separately, but Kono said Tokyo now believed a part of the missile fell away and landed elsewhere in the sea.

North Korea is believed to have developed two Pukguksong missiles, and their maximum flight range was known to be around 1,300 kilometers, according to South Korea’s Yonhap news agency.

Kono declined to comment on whether the missile in question was an SLBM or not, saying Tokyo was still analyzing intelligence.

He said the peak altitude of 900 km was abnormally high, and that Tokyo believes Pyongyang fired the missile on “a lofted trajectory.”

A missile can fly for a longer period if fired on a normal trajectory, while a projectile flying on a lofted trajectory falls much faster — making it extremely difficult for Japan’s anti-missile defense system to shoot it down.

In July, North Korea’s state-run media reported that leader Kim Jong Un had inspected a newly built submarine. Yonhap quoted South Korean intelligence authorities as saying that it seemed to be capable of carrying three SLBMs and was ready to be deployed “soon.”

An analysis by Joseph Bermudez and Victor Cha published on Aug. 28 by Washington-based think tank the Center for Strategic and International Studies concluded that it would still take some time for Pyongyang to develop a truly operational ballistic missile submarine.

“Despite North Korea press statements that ‘operational deployment is near at hand,’ it is more accurate to describe the SLBM existential threat as emerging rather than imminent,” the two argued.

Nevertheless “North Korea is making real progress … bringing them closer to a survivable nuclear force and lessening prospects for full denuclearization,” the article read.

An analysis of commercial satellite images by 38 North, a North Korea monitoring project at Johns Hopkins University, showed that Pyongyang may have been preparing two submersible test stand barges for its SLBM development program in the Nampo Naval Shipyard as of Sept. 18.

Such barges were first observed in 2017 and were subsequently refurbished, according to 38 North.

The South Korea-Japan relationship has been highly strained recently over history issues, which prompted Seoul to announce in August its withdrawal from the General Security of Military Information Agreement (GSOMIA). The pact formally expires on Nov. 23. South Korean Defense Minister Jeong Kyeong-doo reportedly said he had asked Tokyo to share certain intelligence on Wednesday’s missile-firing by North Korea based on GSOMIA.

However, during press briefings in Tokyo, both Suga and Kono declined to comment on whether Tokyo had shared any intelligence with Seoul on Wednesday’s missile-firing.

A key purpose of GSOMIA is to share sensitive intelligence on North Korean missile programs, including radar data, to determine where a missile landed and its trajectory. Experts have raised concern that Seoul’s withdrawal from the pact could hinder smooth communications between Japan, South Korea and the United States.

Staff writer Sakura Murakami contributed to this report.