"You are taking a very important historical responsibility at this critically
Ban called on Kenya's opposing political parties to find common ground in the interests of the country's stability.
"What I'd like to ask you is to look beyond these individual interests, look beyond the party lines, look towards the future, the brighter future of your country."
Ban was talking alongside Kofi Annan, his predecessor, and representatives of negotiating teams for Mwai Kibaki, the Kenyan president, and Raila Odinga, the opposition leader.
The talks are the first between the opposing sides since the elections on December 27.
As international pressure mounted on Kenyan leaders for a negotiated settlement to the crisis, violence has continued unabated.
On Friday, police said they killed four people as a mob looted houses and shops in the western town of Kericho.
John Otieno, heading the criminal investigations in Kericho, said: "Those who were shot and killed were participating in looting properties and torching residential houses and business buildings."
Several people were also killed in fighting in Nyamira district, a police commander said. They were either hacked or shot with poisoned arrows.
'Crime of passion'
On Thursday, David Kimutai Too, an opposition lawmaker, was killed by a policeman in Eldoret. A woman was also killed in the shooting.
Police said Too's death was a crime of passion. They said a traffic police officer had found out that Too was having an affair with his girlfriend and killed the pair.
It was the second death of an opposition MP in three days. The opposition Orange Democratic Movement (ODM) has said that both deaths were political assassinations.
Julius Langat, a spokesman for Too's family, said that the MP was not having an affair with the woman and that he had feared for his safety.
Langat said that the woman was a police officer and Too had met her to seek protection for his family, including his two children.
Violence has been raging in the country after December's disputed election results.
About 1,000 people have been killed in the violence and hundreds of thousands have been displaced.