"The president explained that the Washington Declaration is more effective than multilateral agreements within NATO since it was adopted 'one-on-one.' And it is the first time when the concept of extended deterrence was set out in a written document with a certain country rather than as an oral statement," the spokesman said.
On Wednesday, the leaders of South Korea and the US adopted the Washington Declaration that provides for the establishment of a regular bilateral consultation mechanism called the US-South Korean Nuclear Consultative Group on extended deterrence and strategic planning. South Korea also secured a US promise to promptly deploy "the entire force of the alliance," including nuclear weapons, in the event of a nuclear attack by North Korea.
The US also assured Seoul it would use all measures, including nuclear weapons, in the case of an aggression from North Korea, and promised to send nuclear missile submarines to the Korean Peninsula.
On Friday, the South Korean president stated in a speech at Harvard Kennedy School in Cambridge, Massachusetts, that the declaration should be understood as an "upgraded" version of the 1953 Mutual Defense Treaty singed by Seoul and Washington following the 1950-1953 Korean War.