Nyusi is expected to face opposition from the opposition Renamo Party leader Afonso Dhlakama.
Frelimo and Renamo supporters have fought since a disputed election three years ago.
President Nyusi and Dhlakama met for the first time since 2015 in August, raising hopes for a resolution to the conflict whose scale is difficult to gauge because fighting mostly takes place in the remote interior.
The president told delegates at the ruling party’s conference that he would continue with efforts to pacify the Southern African nation.
“It is an urgent task that belongs to everyone, regardless of political affiliation, religious or social position,” he said.
Members of the current government and Renamo fought on opposing sides in a civil war from 1975 to 1992 that killed an estimated 1 million people.
Frelimo has ruled Mozambique since it gained independence in 1975.