It's one of the four points listed in the joint statement US President Donald Trump and North Korea's Kim Jong Un signed on June 12, the day of their historic meeting in Singapore.
원문출처 : https://www.cnn.com/2018/07/26/asia/north-korea-us-troop-remain-intl/index.html
원문출처 : https://www.cnn.com/2018/07/26/asia/north-korea-us-troop-remain-intl/index.html