South Korea said Thursday it will end an intelligence-sharing agreement with Japan, a move that prompted immediate concern from U.S. military officials in the wake of repeated North Korean missile tests.

A Pentagon spokesman, Lt. Col. Dave Eastburn, said intelligence sharing is key to a united defense strategy in the region. The United States, South Korea and Japan are stronger and safer when they work together, he said.

"The Department of Defense expresses our strong concern and disappointment" with South Korea's decision, Eastburn said in a statement. "We strongly believe that the integrity of our mutual defense and security ties must persist despite frictions" in the South Korea-Japan relationship, he said.

Without the agreement in place, "the United States has to play the middle man between" Japanese and South Korea intelligence agencies, said Kelly Magsamen, vice president for national security and international policy at the Center for American Progress, a liberal think tank.

"In a crisis situation, that is less than ideal," she said. The three countries need to be able to communicate and coordinate "in real time" about any possible threat, said Magsamen, who served as principal deputy assistant secretary of defense for Asian and Pacific Security Affairs in the Obama administration.

South Korea’s presidential office announced the decision to nix the intelligence-sharing pact in retaliation for Japan’s decision to downgrade South Korea’s trade status.

“Under this situation, the government has determined that maintaining the agreement, which was signed for the purpose of exchanging sensitive military intelligence on security, does not serve our national interests,” Kim You-geun, the deputy director of South Korea’s presidential national security office, said in a nationally televised statement.

Japan's foreign minister Taro Kono blasted the decision. "It can only be said that the decision made by the (South Korean) government completely misjudges the current regional security environment, and therefore, it is deeply regrettable."

Kono said the trade dispute should not be linked to the security agreement and said Thursday's action was part of "extremely negative and unreasonable actions" by South Korea.

Thursday's development was the latest in a series of tit-for-tat moves that have frayed relations between the two countries, which have an acrimonious history dating to Japan's colonial rule over South Korea. Japan annexed Korea in 1910 and ruled brutally for 35 years, trying to wipe out Korean culture and forcing thousands of Korean women into prostitution for Japanese soldiers.

The wounds of that history have been reopened by court rulings in South Korea that South Koreans could seek compensation from Japanese companies for forced labor. Secretary of State Mike Pompeo and other top Trump administration officials urged Japan and South Korea to stop the escalating retaliatory actions – to no effect.

The United States played a major role in getting the two countries to sign the intelligence agreement, which went into effect in 2016 and made it easier for the two U.S. allies to share classified data about North Korea’s nuclear threat, as well as to monitor China's escalating military capabilities.

Magsamen said the failure of the Trump administration to save the deal highlights the president's lack of interest in preserving vital U.S. alliances.

"This kind of trilateral engagement requires pretty significant American political engagement," she said. Trump is "willing to fritter away these alliances, and these countries are making their own political calculations based on that."

Pompeo said the Trump administration urges officials in both countries to continue talking.

"There is no doubt that the shared interests of Japan and South Korea are important, and they’re important to the United States of America," Pompeo said during a trip to Canada. "We hope each of those two countries can begin to put that relationship back in exactly the right place."

North Korea has conducted six weapons tests in recent weeks.

South Korea said it would formally notify Japan of its decision before Saturday, the deadline for an extension of the pact for another year.

As the Japan-South Korea dispute spiraled, North Korea said Thursday it would not conduct talks over its nuclear arsenal as long as “military threats” from the United States and South Korea continue. The statement, from North Korea's Foreign Affairs Ministry, said the just-concluded joint U.S.-South Korean military drills and Seoul's acquisition of new stealth fighter jets amounted to “dangerous and unusual military moves.”

Contributing: Tom Vanden Brook and The Associated Press