Lee Jae-myung has been sworn in as South Korea's president, ushering in the nation's first liberal government since 2022.

Lee took the oath of office at the National Assembly on Wednesday.

The 21st president of South Korea pledged to uphold the Constitution, protect the country and pursue peaceful unification of the homeland.

Lee also promised to promote individual freedom, public welfare and the development of national culture. He vowed to fulfill his presidential duties with sincerity.

Lee on Japan, US relations

The new president later delivered a speech in which he said he would strengthen trilateral cooperation among South Korea, the United States and Japan based on Seoul's bilateral alliance with Washington.

Lee also said relations with neighboring countries would be approached from a pragmatic perspective derived from national interests.

Later, he spoke about his country's relations with Japan at his first news conference since assuming office.

Asked about the bilateral relations by a reporter, Lee touched on historical issues and the Takeshima Islands dispute between the two countries.

South Korea controls the islands. Japan claims them. The Japanese government maintains the islands are an inherent part of Japan's territory. It says South Korea is illegally occupying them.

Lee said despite the existence of such issues, the two countries also have "various common interests." He said he thinks South Korea and Japan will be able to explore aspects beneficial to both sides, such as the economy, security and cultural exchanges. He said that doing this "will make it possible to establish friendly ties and thrive together."

On the issues of wartime labor and those referred to as wartime comfort women, Lee said "consistency in policy is important" in the relationship between nations, as a sense of trust between them has to be preserved.

He said unilaterally coercing or pushing ahead with national policy based on personal beliefs is "not easy," and that this reality must be taken into account.

Lee praised the past agreement between President Kim Dae-jung and Prime Minister Obuchi Keizo, apparently referring to the 1998 joint declaration issued by both countries. He said it would be desirable to keep such an international agreement.

Lee also said relations between nations are no different from personal ties. He said each should candidly recognize what they have done, as well as apologize for it, or cooperate and compete with one another. He said he hopes the two countries will be able to build such a "rational" relationship.

Lee on North Korea

Regarding North Korea, Lee said he would respond to nuclear and military provocations with strong deterrence grounded in the US-South Korea military alliance.

But he also said he will open channels of communication with the North and work toward peace on the Korean Peninsula through dialogue and cooperation.

Earlier in the day, Lee spoke by phone with the chairman of the Joint Chiefs of Staff, who briefed him on North Korea's recent military activities.

Lee instructed the top military official to ensure a fully prepared and seamless defense posture based on the US-South Korea alliance.

Lee garnered 49.42 percent of votes, while Kim Moon-soo of the conservative People Power Party took 41.15 percent.

High expectations

South Koreans have high hopes of the new president. A man in his 70s said: "The final result was expected since former President Yoon Suk-yeol made the wrong decision by declaring martial law. I hope the new president will do his job well for the next five years. In particular, I would like to see the implementation of his economic pledges."