Flags of the United States and the U.S. Department of Energy fly near the department's headquarters in Washington, Feb. 14. AFP-Yonhap

The U.S. government's recent move to designate Korea as a "sensitive country" in the energy sector is seen as a subtle warning amid growing calls within Korea to develop its own nuclear arsenal, analysts said, Tuesday.

According to diplomatic sources, the U.S. Department of Energy (DOE) is reviewing whether to classify South Korea as a sensitive country on its internal list, a measure that will take effect on April 15.

A "sensitive country" is one that requires "particular consideration for policy reasons, including national security, nuclear nonproliferation, regional instability, threats to national economic security, or support for terrorism," according to the DOE website.

The department reportedly notified its affiliated institutions in early March that, in addition to existing countries such as India, Israel, Pakistan and Saudi Arabia, four new countries — including South Korea— would be added to the list.

The Ministry of Foreign Affairs became aware of this through "unofficial channels" as the U.S. did not disclose the move in advance through diplomatic channels.

"According to the latest information from the South Korean Embassy in the U.S. and the U.S. Embassy in South Korea, the decision has not been finalized yet," Foreign Minister Cho Tae-yul said during a National Assembly session.

When asked whether he had received prior notice from the U.S. side regarding the issue, Cho replied, "I believe not. The U.S. did not inform us in advance, so we became aware of it through unofficial channels."

The foreign ministry is reaching out to the DOE for detailed information behind its move, with diplomatic efforts expected to follow to prevent the country from being formally listed.

Foreign Minister Cho Tae-yul, right, speaks during a parliamentary session at the National Assembly in Seoul, Tuesday. Yonhap

This marks the first time that South Korea, a key Asian ally of the U.S., has been potentially classified as a sensitive country by U.S. energy authorities.

Once designated, cooperation between South Korea and the U.S. in advanced technology fields such as nuclear energy and artificial intelligence (AI) may be limited, as researchers from sensitive countries must undergo stricter certification procedures to enter DOE facilities or participate in joint research projects.

Diplomatic observers view this as a sign that the Donald Trump administration is growing wary of rising support within Korea for it to go nuclear.

"It is unclear exactly why the U.S. has taken this step, but given the current circumstances, this could be a warning from the Trump administration about the increasing calls within political circles for the redeployment of U.S. tactical nuclear weapons or for independent nuclear armament," said Yang Moo-jin, president of the University of North Korean Studies.

Calls for South Korea to obtain its own nuclear weapons have gained traction amid rising doubts about the effectiveness and commitment of U.S. extended deterrence against North Korea's growing nuclear threats, particularly among conservative politicians and researchers. The idea has gained further momentum since Trump's return to office, as the president has repeatedly hinted at reducing U.S. extended deterrence by accusing South Korea of free-riding on security.

Yang added that if South Korea is designated as a sensitive country, it could affect bilateral cooperation in nuclear energy and damage the country's international reputation.

"The government should clarify its stance not to pursue nuclear weapons to prevent this move from taking effect," he said.

Park Won-gon, a professor of North Korean studies at Ewha Womans University, said, "It needs to be clarified why the DOE made this decision, as nuclear issues on the Korean Peninsula are handled primarily by the U.S. State Department."

He noted that among the reasons cited by the DOE for classifying a nation as "sensitive," nuclear proliferation is likely the main concern for the U.S. regarding South Korea.

"Trump is unlikely to accept South Korea's nuclear ambitions," Park said. "Although his foreign policies are unorthodox and unpredictable, he will not risk allowing Seoul to go nuclear. Once South Korea obtains its own nuclear arms, U.S. influence over the Korean Peninsula will be de facto diminished."

These developments come as conservative politicians continue to rally for the potential of nuclear weapons. At a forum hosted by Rep. Yu Yong-weon of the ruling People Power Party (PPP), Tuesday, Seoul Mayor Oh Se-hoon, a conservative heavyweight, reiterated his support for developing a domestic nuclear arsenal.

"Why can't we exercise our rights within the scope of the Nuclear Non-Proliferation Treaty? We should demand it from the U.S.," the mayor said.