Southern separatists were defeated in a 1994 civil war waged between the former northern and southern Yemeni states.
Ali Abdullah Saleh was declared president of a united Yemen in 1990. Political grievances eventually led to civil war threatening the nation's unity.
The Yemeni government said it was operating according to the terms of a national reconciliation agenda by issuing an apology for the 1994 conflict.
The government said it was issuing the apology on behalf of former regimes. It said the previous administration bore "primary responsible, and not the only one, for the wars and consequent repercussions," the official Saba News Agency reported Wednesday.
Yemeni President Abdo Rabu Manour Hadi took power in 2012 after longtime President Saleh stepped down in the wake of the Middle East and North African upheavals known as the Arab Spring.
Hadi in July told U.S. Secretary of State John Kerry more than 500 delegates were taking part in the reconciliation agenda.