President Moon, who advocates greater dialogue with South Korea's neighbours, then put forward the idea of a wider unified Olympic squad.
The report notes that the plotters considered arranging accidents, with a auto accident or the derailment of a train carrying Kim Jong-un on the table.
Having witnessed the launch 200 kilometers (124 miles) southwest of Seoul, Moon said he had "personally confirmed that the people may be at ease" following a series of North Korean missile tests this year alone.
Jang Woong, North Korea's sole member of the International Olympic Committee (IOC), together with a North Korean delegation of athletes, also attended the sports ceremony in Muju town on Saturday.
In his speech, Moon said he'd once again like to feel the emotions from watching the joint march of the two Koreas at the Opening Ceremony of the Sydney 2000 Olympics.
Before his speech, Moon shook hands with Chang and exchanged a few words with him.
Dr Go Myong Hyun, research fellow at The Asan Institute for Policy Studies, said Mr Moon will take to the White House a message to shift the focus from military containment, which includes annual joint exercises and deployment of strategic assets, to dialogue with the North.
Plans were also laid out for a staged coup to secure a friendly puppet-regime in North Korea, it has been reported.
Last week, South Korea's Culture, Sports and Tourism Minister Do Jong Hwan said that North Korea's "top-class" Masikryong Ski Resort could be a potential venue for events in next year's Pyeongchang Winter Olympics.
South Korea took the first two gold medals in the 2017 World Taekwondo Championships on Sunday with victories for both the men and women. "If South Korea truly wants to improve the Korean ties and seek peace, it should stop picking on our nuclear deterrent force and stand against the U.S.'s plot for first nuclear strike on the North".
According to the letter, after more than a decade of searching unsuccessfully for Sneddon it is time for America to consider the possibility that the North Korean government was directly responsible for David's disappearance.
Organisers of Pyeongchang 2018 have urged it to take part to make them a "peace Olympics".
The president was speaking at the opening of the World Taekwondo Championships in the southern county of Muju.