The presidential office in Seoul said President Moon Jae-in and North Korean leader Kim Jong Un reached such an agreement during several rounds of exchanges of letters since April.
The Blue House says the two Koreas tested their communication channel on Tuesday morning.
North Korean leader Kim Jong Un, left, poses with South Korean President Moon Jae-in for a photo inside the Peace House at the border village of Panmunjom in Demilitarized Zone, South Korea on April 27, 2018. (Korea Summit Press Pool via AP, File)
The development comes amid more than two years of a stalemate in U.S.-led diplomacy aimed at stripping North Korea of its nuclear weapons.