An American nuclear-powered aircraft carrier arrived in South Korea today, Saturday, to conduct a trilateral exercise involving Japan as part of intensified military training to counter North Korean threats, which have escalated following a security agreement with Russia.

The arrival of the USS Theodore Roosevelt strike group in Busan came a day after South Korea summoned the Russian ambassador to protest a significant agreement between Russian President Vladimir Putin and North Korean leader Kim Jong Un this week.

The agreement stipulates mutual defense assistance in the event of war. South Korea claims the deal poses a threat to its security and warned that it may consider sending weapons to Ukraine to help combat the Russian invasion in response, a move that would certainly damage its relations with Moscow.

Following a meeting between their defense ministers in Singapore earlier this June, the United States, South Korea, and Japan announced the "Freedom's Edge" exercises.

The Roosevelt strike group will participate in drills expected to start during June. The South Korean military did not immediately confirm specific details about the training.

Christopher Alexander, commander of the ninth carrier strike group, stated that the exercises aim to sharpen the tactical proficiency of the vessels and enhance interoperability between the naval forces of the countries "to ensure our readiness to respond to any crisis or emergency."

The South Korean Navy said in a statement that the arrival of the aircraft carrier demonstrates the strong defensive posture of the allies and "the rigorous readiness to respond to advancing North Korean threats." The carrier's visit comes seven months after another American aircraft carrier, the USS Carl Vinson, came to South Korea in a show of force against North Korea.

The Roosevelt strike group also participated in a trilateral maneuver with South Korean and Japanese naval forces in April in the disputed East China Sea, where concerns are increasing over China's territorial claims.

In the face of growing North Korean threats, the United States, South Korea, and Japan have expanded their joint exercises and reinforced the visibility of American strategic military assets in the region in an effort to intimidate the North. The United States and South Korea are also updating their nuclear deterrence strategies, as Seoul seeks stronger assurances that Washington will swiftly and decisively use its nuclear capabilities to defend its ally against a North Korean nuclear attack.