"[The summit] will become a critical turning point for the complete denuclearization of the Korean Peninsula and peacemaking process," Korean news agency Yonhap quoted Moon as telling a meeting with presidential secretaries and aides.
U.S. President Donald Trump and North Korean leader Kim Jong-un are slated for a second summit on Feb. 27-28 in Vietnam.
"[The summit] will serve as an opportunity for the Koreas to elevate their ties," Moon added.
The Vietnam summit will be the second such meeting between the two leaders after the Singapore summit held last year which aimed at halting the nuclear programs of Pyongyang and lifting of UN sanctions on the country.
Pyongyang has been seeking relief from UN sanctions to “boost trust” ahead of the planned summit.
Meanwhile, Seoul-based The Chosunilbo newspaper reported Monday that the UN Security Council has granted relatively generous exemptions from sanctions for humanitarian aid to North Korea.
"This may be a deliberate step on the part of the U.S., a permanent member, to entice North Korea into giving up its nuclear program," the newspaper said.