Kim Dong-hyun and Han Sang-mi contributed to this report, which originated with VOA’s Korean Service.

WASHINGTON — Seoul’s decision to end a military intelligence pact with Tokyo could have far-reaching consequences that could put its own security at risk, reducing its ability to defend against potential North Korean aggression, experts say.

Seoul announced Thursday it would terminate an intelligence-sharing agreement with Tokyo, attributing the move to Japan’s decision to remove South Korea from its “white list” of favored trading partners earlier this month.

Japan’s decision “brought about fundamental changes to the environment for security cooperation between the two countries,” Kim You-geun, deputy director of South Korean National Security Council, said Thursday.

FILE - Plaintiffs' attorneys Lim Jae-sung, right, speaks as Kim Se-eun listens during a press conference in Tokyo, Dec. 4, 2018. Lawyers for South Koreans forced into wartime labor have taken legal steps to seize the South Korean assets of a Japanese company.

Trade feud, historical animosity

Seoul and Tokyo have been escalating a trade feud since early July. The disagreement is rooted in historical animosity stemming from Japanese companies’ use of South Korean forced labor during its colonial rule on the peninsula and during World War II.

The termination announcement came a day before a deadline Saturday of a 90-day notice period for one side to tell the other if it intends to cancel the arrangement. The deal automatically renews annually if no notice is given.

Pentagon spokesman Lt. Col. Dave Eastburn, in an email sent to VOA Thursday, urged the two U.S. allies to work together, emphasizing, “Intel sharing is key to developing our common defense policy and strategy.”

What is GSOMIA?

Under the bilateral accord, known as the General Security of Military Information Agreement (GSOMIA), signed in 2016, South Korea and Japan agreed to exchange sensitive military information to respond more efficiently to potential threats posed by North Korea, China and Russia. Washington has separate intelligence-sharing deals with both countries.

David Maxwell, a former U.S. Special Forces colonel and current fellow at the Foundation for Defense of Democracies, said South Korea would suffer “the worst” from its decision to terminate the agreement that would impede the trilateral cooperation in the region.

FILE - North Korea test-fires a weapon in this undated photo released Aug. 16, 2019, by the Korean Central News Agency. Pyongyang conducted another launch Aug. 23, violating a promise to U.S. President Donald Trump to refrain from such tests.

The end of the agreement, according to Maxwell, means the three countries will be hampered in their ability to have open three-way talks on detecting early warning signs of North Korea’s missile launches, countering its weapons proliferation, and conducting operations against its sanctions evasion.

Although information can be shared using the U.S. as an intermediary, the flow will be slow or severed if South Korea or Japan asks the U.S. not to share its information with the other, Maxwell added.

“This plays into Kim Jong Un’s (and Chinese and Russian) hands to disrupt U.S. alliance,” he said.

While testing missiles this month, North Korea called on South Korea to abandon its intelligence pact, signed with Japan under the conservative government of Park Geun-hye, who preceded current South Korean President Moon Jae-in.

“It is rather abnormal that the agreement of betraying the country signed by Park Geun-hye … still exists without being abrogated,” said North Korea’s propaganda outlet, Uriminzokkiri.

FILE - A woman walks past an advertisement featuring Japanese and South Korean flags at a shop in the Shin Okubo area in Tokyo, Aug. 2, 2019.

Dangerous consequences

Terminating the pact could have dangerous consequences if a crisis erupted on the Korean Peninsula, said Bruce Bennett, a senior defense analyst at the Rand Corp. An example would be if American troops would need to be brought from the U.S. and routed through Japanese air force bases, requiring three-way communications through a confidential network.

“That’s all going to be coordinated very closely,” Bennett said. “It’s not going to be coordinated by open radio calls … that would tell North Korea what to hit next. So we need to have the GSOMIA to be able to coordinate in a classified manner in terms of the deployment of U.S. forces. And that’s what the South Korean government is risking by saying it won’t renew the GSOMIA.”

Bennett, citing a South Korean military white paper, said the U.S. would need to bring about 690,000 troops to South Korea during a conflict with North Korea. The estimated number is more than the 28,000 American soldiers stationed in South Korea.

South Korea has about 17 airfield bases that can be used to bring in troops from the U.S. during wartime, Bennett said, but they are “not an adequate [number of] airfield structures to deploy forces rapidly.”

South Korea has 20 airfields, but among them, Gimpo and Incheon are within North Korean artillery range and thus cannot be used to land U.S. forces, Bennett said, adding that another airfield on Jeju Island would not be suitable either if the troops needed to fight on the peninsula.

“Are we going to have arrangements with Japan to help us use Japan’s bases and infrastructure to bring those forces to Korea?” Bennett asked. “Because if we don’t, that’s going to significantly slow the ability of U.S. forces to get to Korea and could put Korea at a disadvantage for a period of time.”

Seoul decided to scrap the intelligence-sharing agreement despite these risks, Bennett said, because it believes it will “be able to peacefully coexist with North Korea.” He added South Korea “doesn’t have other places where it’s got a lot of leverage on the Japanese” as a way to retaliate against Tokyo in their trade dispute.