Minister of Science and ICT Yoo Sang-im, left, and Foreign Minister Cho Tae-yul attend a Cabinet meeting at Government Complex Seoul, Tuesday. Joint Press Corps

The Korean and U.S. governments have shown differing views on Washington's decision to designate Seoul as a "sensitive country" in the energy sector.

Korean authorities consider the designation a matter serious enough to escalate into a significant diplomatic rift and are working quickly to have the designation removed before it takes effect on April 15. Meanwhile, U.S. officials have downplayed the issue, calling it "not a big deal" and insisting that the decision will not impact bilateral cooperation.

"Inclusion (on the list) does not necessarily indicate an adversarial relationship with the United States; many designated countries are those we regularly cooperate with on a variety of energy, science, technology, counterterrorism and nonproliferation issues," a U.S. Department of Energy (DOE) spokesperson told The Korea Times via email, Wednesday.

The spokesperson added that the designation "does not prohibit Americans or DOE personnel from visiting or doing business with listed countries, just as it doesn't prevent these foreign nationals from visiting DOE sites.

"The designation does not prohibit scientific or technical cooperation. These visits and cooperation undergo an internal review beforehand."

The comments come after the DOE's January decision to add Korea to a list of sensitive countries, which already includes 25 nations, such as China, Russia and Iran. Once added, Korea will be the only formal U.S. ally on the list with which Washington has a mutual defense treaty.

Caught off guard by the decision, the Korean government has been acting swiftly to assess the potential fallout and push for the reversal of the designation. Researchers have raised concerns about potential increased difficulty in accessing information and visiting DOE-affiliated laboratories as a result of the decision.

Joseph Yun, acting U.S. ambassador to Korea, speaks during an event in Seoul hosted by the American Chamber of Commerce in Korea, Tuesday. Yonhap

Amid these developments, U.S. Charge d'Affaires to Korea Joseph Yun, the acting ambassador to Korea, downplayed the issue, calling it "not a big deal."

"I'm just sorry that this whole thing got out of control ... as if it is a big deal. It is not a big deal, and I've been trying to find out exactly what it is and why it happened," Yun said at an event hosted by the American Chamber of Commerce in Korea on Tuesday.

Yun suggested that Korea's inclusion may have been prompted by incidents involving the mishandling of sensitive information at DOE-affiliated laboratories, but stressed that the decision would not affect bilateral cooperation.

This apparent dismissal by a senior U.S. diplomat contrasts with Korea's Ministry of Foreign Affairs, which said that it is treating the issue "seriously" and is working closely with the science and industry ministries to address it.

Placing a key Asian ally on a list typically reserved for adversaries, while dismissing it as "not a big deal," has also raised further questions about the underlying motives.

According to the foreign ministry, the U.S. side has confirmed that the decision was driven by security concerns rather than Korea's foreign policy, as there had been speculation that the designation resulted from growing calls here for the development of its own nuclear arsenal. The ministry declined to confirm what security breaches led to the decision or if Washington has specifically pointed to any security incidents.

"It may seem like a minor decision from the U.S. government's perspective, but for us, it has significant implications for diplomacy and technological research, as the designation could serve as the basis for further limitations or potential sanctions," said Jun Bong-geun, professor emeritus at the Korea National Diplomatic Academy.

"Security breaches typically result in penalties for individuals or institutions, but it is rare for the U.S. to escalate the issue to the national level, where an entire country faces penalties."

The foreign ministry said it is in close consultation with U.S. authorities on the issue but declined to comment on the possibility of Korea's removal from the list.

When asked whether Seoul and Washington differ in their assessment of the situation's gravity, a ministry official said, "The U.S. has said that even if Korea is on the list, it will not have a significant impact on our joint research and technological cooperation."