The President announced on December 26, 1976, on the third day after the signing of the Tripoli Agreement, that a plebiscite would be conducted in the thirteen provinces to determine which of them would want to be part of the autonomous region. He stressed that this is in keeping with the Philippine government position that any settlement in Mindanao must be in full accord with constitutional processes.

Source: B.R. Rodil Kalinaw Mindanao; The Story of the GRP-MNLF Peace Process, 1975-1996