Kenneth D. Kaunda, chairman of the Organization of African Unity, will mediate a bloody border dispute between Uganda and Kenya in response to an appeal by Ugandan President Yoweri Museveni. The appeal followed clashes during the last week in which Uganda reported three soldiers and 10 civilians slain. Kenya said its forces killed 30 Ugandan soldiers but mentioned no casualties of its own. Kaunda said he will meet soon with Museveni and President Daniel Arap Moi of Kenya. "I am praying very hard that nothing worse happens between the two countries," said Kaunda, who is president of Zambia.