President Yoon Suk Yeol made an unprecedented tour of a U.S. nuclear-capable ballistic missile submarine (SSBN) on Wednesday.

During the tour, he warned that South Korea and the United States will respond “overwhelmingly” and “resolutely” to North Korea’s nuclear and missile threats.

Yoon became the first leader of a U.S. allied country to inspect an American SSBN when he visited the USS Kentucky, currently making a port call at a naval base in Busan.

It’s the first time in 42 years that a U.S. nuclear-powered submarine has visited Korea.

“It is meaningful and reassuring to visit the USS Kentucky, one of the most powerful strategic assets in existence,” Yoon said, adding that the deployment “demonstrates the two countries’ intentions to routinely deploy U.S. strategic assets and defend extended deterrence capabilities.”

Yoon offered words of encouragement to South Korean and American troops, who he called “defenders of freedom and peace” in Korea.

“South Korea and the United States will continue to respond overwhelmingly and resolutely to North Korea’s nuclear and missile threats through the regular deployment of strategic assets, such as SSBNs, and the Nuclear Consultative Group,” Yoon said.

The USS Kentucky arrived on the peninsula on Tuesday, coinciding with a visit by U.S. White House National Security Council (NSC) officials to launch the inaugural Nuclear Consultative Group (NCG) meeting in Seoul.

Early Wednesday, North Korea fired two short-range ballistic missiles into the East Sea in apparent protest of the arrival of the American nuclear-powered submarine and the NCG meeting.

Yoon noted that through the NCG, South Korea and the United States agreed to discuss joint planning and execution of U.S. nuclear operations, combining nuclear and other assets to “enhance the visibility of the deployment of U.S. strategic assets around the Korean Peninsula.”

The NCG is a bilateral consultative body aiming to strengthen U.S. extended deterrence commitment to South Korea using the full range of its military capabilities, including nuclear weapons, to defend its ally.

The NCG was established as a part of the Washington Declaration, an agreement between the two countries to mark the 70th anniversary of the alliance during a bilateral summit Yoon and U.S. President Joe Biden in April.

On Wednesday’s tour of the SSBN, Yoon was accompanied by first lady Kim Keon-hee and aides including National Security Adviser Cho Tae-yong, and greeted by Gen. Paul LaCamera, commander of the U.S. Forces Korea (USFK), Cara Abercrombie, deputy assistant to the president and coordinator for defense policy and arms control, and other American diplomats and military officials.

The arrival of the 18,750-ton Ohio-class SSBN, a key U.S. strategic asset, is seen as a demonstration of the two countries ironclad combined defense posture. The 170-meter long Kentucky was escorted by two U.S. guided missile destroyers.

The USFK said in a statement that the visit “reflects the United States’ ironclad commitment to the Republic of Korea,” referring to the South’s official name, and demonstrates the “flexibility, survivability, readiness, resolve, and capability of the U.S. Navy submarine forces.”

The USS Kentucky, one of 14 U.S. submarines capable of carrying ballistic missiles, is known to hold 20 Trident II D5 missiles, each of which can deliver up to eight nuclear warheads to targets as far as 12,000 kilometers away.

The last U.S. ballistic missile submarine to make a port call in Korea was the USS Robert E. Lee in 1981.

The first bilateral NCG meeting was co-chaired by Kim Tae-hyo, Korea’s principal deputy national security adviser, and Kurt Campbell, the White House NSC coordinator for Indo-Pacific affairs, known as the key architect of the U.S. pivot to Asia strategy during the Barack Obama administration.

The two countries issued a joint statement after the NCG meeting Tuesday that warned that “any nuclear attack by North Korea against the United States or its allies is unacceptable and will result in the end of that regime,” and that any such attack against South Korea will be “met with a swift, overwhelming, and decisive response.”

Washington’s demonstration of its nuclear umbrella commitments to allies in the region comes as some South Korean politicians urge the country to develop its own nuclear arsenal.

Last week, North Korea launched an intercontinental ballistic missile (ICBM) into the East Sea, However, the 15-member UN Security Council was unable to come up with joint action due to the vetoes of permanent members China and Russia, who traditionally have sided with North Korea.

BY SARAH KIM [kim.sarah@joongang.co.kr]