Chung Eui-yong, chief of South Korea's Presidential National Security Office, speaks to reporters on May 5, 2018, at Incheon International Airport after wrapping up his visit to Washington (Yonhap)

Chung made the remarks upon arriving at Incheon International Airport, after his visit to Washington to meet his US counterpart, John Bolton.

Earlier in the day, the White House said South Korean President Moon Jae-in and US President Donald Trump will meet in Washington on May 22, ahead of Trump's meeting with North Korean leader Kim Jong-un.