President Yoon Suk Yeol on Tuesday denounced a pact signed between North Korea and Russia last week as "an anachronistic act" that goes against the progress of history and Pyongyang's repeated provocations as "despicable and irrational."

During his televised speech to mark the 74th anniversary of the outbreak of the Korean War on June 25, 1950, Yoon said the pact, which forges stronger military and economic cooperation between Pyongyang and Moscow, "blatantly violates the United Nations Security Council resolution" designed to contain North Korea through sanctions.

Pyongyang has in recent years been suspected to have illicitly developed nuclear weapons that could in theory reach as far as the US mainland.

Yoon in his speech described North Korea, which invaded South Korea in 1950, as the "the only place on Earth that remains frozen in time," continuing to advance its nuclear and missile capabilities and carry out endless provocations, including floating trash balloons over to South Korea.

Russian President Vladimir Putin signed the pact with his North Korean counterpart Kim Jong-un on June 18. In response, Yoon's office discussed follow-up measures at a meeting of the National Security Council, a presidential advisory body, which included Seoul's reconsideration of arms support to Ukraine.

Yoon publicly denounced the Moscow-Pyongyang pact for the first time on Tuesday after it was forged last week.

Later in the afternoon, Yoon went to Busan to visit nuclear-powered US aircraft carrier the USS Theodore Roosevelt, anchored in the southeastern port city, for a three-way military exercise involving South Korea, the US and Japan. Yoon was the third South Korean President to have boarded a US aircraft carrier, after the late Presidents Park Chung-hee in 1974 and Kim Young-sam in 1994, according to the presidential office.

The visit by the US aircraft carrier to South Korea is a part of implementation measures of the "Washington Declaration" adopted by US President Joe Biden and himself, he said, adding that it symbolizes "the steadfast US defense commitment, including robust extended deterrence."

He emphasized that the alliance with the US is stronger than ever enough to defeat any adversary, saying that North Korea is threatening peace on the Korean Peninsula by advancing its nuclear and missile capabilities and professing the possibility of preemptive use of nuclear weapons.

North Korea incorporated into its constitution in September last year a 2022 law specifying the conditions for the use of nuclear weapons, with Kim holding all the authority to make such a decision.

Later on Tuesday, Russia's Deputy Foreign Minister Andrey Rudenko was quoted as saying by Russian state media outlet Sputnik that Seoul "will accept the new agreement with an understanding, and a sound approach will prevail there, including in relations with Russia," and that Russia was expecting Seoul to accept the pact between Pyongyang and Moscow.

Last week, national security adviser Chang Ho-jin unveiled Seoul's plans to impose sanctions on four vessels, five organizations and eight individuals allegedly involved in the exchange of weapons and oil between North Korea and Russia.

Chang criticized the two countries for initiating the 1950-53 Korean War and the war in Ukraine, respectively, for promising military cooperation to each other based on the assumption of an armed invasion that has not occurred, calling it "irresponsible rhetoric."

South Korea is still technically at war with North Korea, as the two sides reached an armistice in July 1953 after two years of armistice negotiations between officials from not only the two Koreas but also the US, China, the then-Soviet Union and United Nations forces. Military conflict persisted for more than three years.

Seoul estimates that the Korean War resulted in some 140,000 casualties in South Korea's armed forces, and 40,000 more soldiers from South Korea's allies -- including the United States and the United Nations Forces -- were killed on the battlefield. Nearly 1 million South Koreans were either dead, massacred, abducted or missing.

Yoon said Tuesday the South Korean government would work to prevent a repeat of the tragedy to protect the citizens' lives and the principles of freedom and democracy, while its military forces will maintain a readiness posture to overwhelmingly and boldly react to North Korea's provocation.

Yoon honored the fallen heroes of the Korean War as people who laid the foundation for South Korea's prosperity. The country's gross national income per capital surged nearly 600-fold in seven decades, he said.

Tuesday's event in Daegu marked the first that the Korean War commemoration ceremony was held outside of Seoul, South Korea's capital city, according to Yoon's office. Daegu, a city about 230 kilometers southeast of Seoul, served as one of the bastions against North Korea's invasion of the South. The president pledged to nurture the environment in which war veterans gain respect from others.