President Yoon Suk Yeol, left, shakes hands with U.S. President Joe Biden as they meet in the Oval Office of the White House, April 26, 2023, in Washington, D.C. AP-Yonhap

The Korean government is likely to come under criticism over its diplomatic failure to timely respond to the U.S. Department of Energy's decision under the previous Biden administration to list South Korea as a "sensitive country."

The development raised concerns about South Korea's capability to maintain close communication with Washington and ensure diplomacy as the designation came amid a leadership vacuum triggered by impeached President Yoon Suk Yeol's failed martial law attempt, Dec. 3.

The Department of Energy (DOE) put South Korea in the lowest category of its "sensitive and other designated countries list" (SCL) in early January under the Biden administration, and since then, there have been no new restrictions on bilateral science and technology cooperation with the Asian ally, the DOE spokesperson told Yonhap News Agency on Friday (U.S. time).

If the move goes into effect April 15, it could make it harder for South Korea to participate in U.S. research on advanced technologies, such as atomic energy, artificial intelligence and quantum technology.

Seoul's foreign ministry does not appear to have grasped the situation surrounding the DOE's decision until recently as its first reaction Monday to a related news report was that the government is "verifying the matter with related ministries."

"As far as I know, the DOE's sensitive country list has not yet been finalized," foreign ministry spokesperson Lee Jae-woong told a press briefing Thursday, saying South Korea is in "close consultation" with the U.S. on the matter.

Foreign Minister Cho Tae-yul told a National Assembly session earlier this week that South Korea has been "informally" told the DOE was considering categorizing it as a "sensitive country" and has raised the issue with the DOE.

"As far as I know, once the U.S. grasps the situation internally, it may come to us and discuss it," he said.

In the midst of political turmoil, sparked by Yoon's martial law bid and his subsequent impeachment, the South Korean government has stressed the Seoul-Washington alliance remains "ironclad."

But the South Korean government does not appear to have had any clue about the DOE's move in the early stage even though the designation could deal a blow to Seoul's efforts to seek deeper cooperation with Washington in nuclear energy and other sectors.

Foreign Minister Cho Tae-yul, left, speaks during a meeting with lawmakers at the National Assembly in Seoul, March. 11. Yonhap

It remains unknown why the Biden administration decided to place South Korea on the SCL. The decision came amid concerns in Washington over growing voices in South Korea to consider its own nuclear armament in the face of North Korea's evolving nuclear threats.

When a news report about the DOE's possible designation first emerged earlier this week, many had thought the department probably reviewed it under the Trump administration.

But as the DOE decision was made under the Biden administration, some experts raised the possibility that political turmoil caused by Yoon's martial law may have affected the DOE's designation.

The SCL refers to a group of countries to which "particular consideration is given for policy reasons during the DOE internal review and approval process for access by foreign nationals," according to the DOE website.

Countries may appear on the list for national security, nuclear nonproliferation or terrorism support reasons, it said. The list includes North Korea, China and Russia.

In January, then U.S. National Security Adviser Jake Sullivan under the Biden administration described Yoon's botched martial law as "shocking" and "wrong," while voicing confidence that "structurally," the South Korea-U.S. alliance is "incredibly healthy."

If the DOE's designation takes effect as scheduled, it is likely to test the Seoul-Washington alliance under U.S. President Donald Trump, known for his "transactional" approach to alliances, experts said. (Yonhap)