The presidential office has touted the Washington Declaration as the biggest achievement of President Yoon Suk Yeol's state visit to the U.S. and described the new nuclear deterrence agreement with the U.S. as an upgraded version of the 1953 Mutual Defense Treaty.

In a briefing at a press center in Boston on Friday, top office spokesperson Lee Do-woon said it's the first time that the U.S. has declared on paper its extended deterrence pledge to an individual country.

Lee said that through the declaration, the two sides have strengthened their strategic security alliance against North Korea's ever evolving threats and Washington's commitment to the nuclear defense of South Korea cannot be more clear.

He said the declaration is not unilateral but involves joint information sharing, joint planning and joint execution, for which the Nuclear Consultative Group including the two sides' presidential offices and foreign affairs, defense and intelligence authorities has been formulated. 

Lee said Yoon's state visit is significant in terms of taking stock of the achievements of the past 70 years of the alliance and crafting the vision for the next 70 years.

The spokesman said that through the summit and his speech on Capitol Hill, the president conveyed a message of alliance and freedom, two key topics upon which the two nations formed complete agreement.

Lee mentioned supply chain cooperation in high-tech sectors such as artificial intelligence, quantum science, cyber space and outer space as the second notable accomplishment the state visit has produced.

An agreement to sharply expand exchanges between the younger generations through scholarship and visa waiver programs was cited as the third accomplishment.

Lee said Yoon's visit overall was a confirmation of an elevated alliance that goes beyond a bilateral relationship but seeks joint leadership on the world stage for global freedom, peace and prosperity.