Joseph Yun, the acting U.S. ambassador to South Korea, speaks at a business forum hosted by the American Chamber of Commerce in Korea in Seoul, March 18. Yonhap

The designation of South Korea as a sensitive country by the United States was due to "mishandling of sensitive information" during exchanges between science research institutions under the U.S. Department of Energy (DOE), the acting American ambassador to Seoul said Tuesday, calling it "not a big deal."

According to the DOE last week, South Korea was placed in the "lowest" category of the department's "sensitive and other designated countries list" (SCL) in early January.

The designation made recent headlines in South Korea, as it was made during the final weeks of former U.S. President Joe Biden's administration and shortly after President Yoon Suk Yeol imposed martial law in December.

Some observers in Seoul had speculated that the decision may have been influenced by recent discussions in South Korea's political circles calling for Seoul's nuclear armament.

Joseph Yun, the acting U.S. ambassador to Seoul, suggested that the DOE listing was not a serious matter affecting bilateral relations, saying "this whole thing got out of control" and the matter was "not a big deal."

"And I've been trying to find out exactly what it is. Essentially the sensitive country list is confined to DOE laboratories. As you know, the DOE has a number of laboratories," Yun said at a business conference hosted by the American Chamber of Commerce in Korea (AMCHAM).

According to Yun, there were over 2,000 Korean students, researchers and government workers visiting these laboratories last year, some of which have sensitive material.

The acting ambassador explained that Seoul was put on the DOE list due to "some mishandling of sensitive information" that should not be taken out of laboratories but stopped short of elaborating further.

Yun said the DOE list issue was something he had "never heard of" before and only found out about it a few days ago himself.

In addition, the acting ambassador highlighted that South Korea and the U.S. agreed to cooperate as a tier 1 country in fields of advanced science, and stressed that suggesting the listing as having implications in practical research cooperation was "simply wrong."

On Monday, Seoul's foreign ministry said South Korea's placement on the SCL was because of security issues related to DOE-affiliated research institutions rather than a broad foreign policy decision.

The U.S. government is said to have told the ministry that South Korea's SCL inclusion was imposed due to violations of security regulations during South Korean researchers' visits to DOE laboratories or participation in joint research projects.

Joseph Yun, right, acting U.S. ambassador to South Korea, and James Kim, chairperson of the American Chamber of Commerce in Korea (AMCHAM), speak at a business forum hosted by AMCHAM in Seoul, March 18. Yonhap

According to a report from the DOE's Office of the Inspector General (OIG) to Congress, a contract worker at the Idaho National Laboratory (INL) was terminated between Oct. 1, 2023, and March 31, 2024, after the person attempted to board a flight to South Korea with export-controlled information on nuclear reactor design software.

Regarding Pyongyang, the acting ambassador said he believes U.S. President Donald Trump "wants to negotiate and reach a deal with North Korea," saying Trump "has never said a bad thing" about North Korean leader Kim Jong-un.

"I have no doubt he wants to (reach a deal with North Korea). How he does it is still up in the air," Yun said, while noting that key positions at the state and defense departments that handle Korean affairs need to be filled under the current U.S. administration to engage with Pyongyang in earnest.

He also touched on the topic of Trump's tariff policies, saying the measures will "create new opportunities for people bringing goods and services from America" to South Korea, especially in the agriculture, digital and services sectors.

The envoy suggested Seoul take proactive measures, such as opening up particular sectors or reducing non-tariff barriers, to respond better against Washington's country-by-country reciprocal tariffs, expected to be rolled out in April.

He also pointed to the shipbuilding sector as being the field "that's going to be huge" for South Korean companies in the U.S. in the near future, highlighting Hanwha Ocean's recent purchase of an American shipyard in Philadelphia and the company's maintenance, repair and overhaul (MRO) deal with the U.S. Navy. (Yonhap)