The two men will jointly support the team in the evening match in Gangneung against Switzerland, the Yonhap news agency reported, citing Seoul's presidential Blue House.
It did not mention Kim Yo Jong, the young but influential sister of the North's leader Kim Jong Un, who is also part of Pyongyang's delegation and has been the focus of widespread attention.
The report could not immediately be confirmed, but pictures showed both Kim Yong Nam and Kim Yo Jong at Seoul railway station taking a high-speed train to Gangneung -- along with the South's unification minister, who is in charge of relations with the North.
"We are not giving any information on the itinerary of President Moon in advance," a spokesman told AFP.
The unified women's ice hockey team is the first time the two Koreas will compete on the same side for 27 years, and comes after their athletes marched together behind a unification flag at Friday's opening ceremony.
But the team's formation has provoked a backlash in the South, with critics saying Seoul was depriving its own citizens of the chance to compete on the Olympic stage in its attempts to engage with the North.
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