1. Central Tapanuli

1. Central Tapanuli
2. North Tapanuli
3. Toba Samosir

Regencies expected to join East Sumatra province:

1. Asahan
2. Deli Serdang
3. Karo
4. Langkat
5. Labuhan Batu

Undecided regencies:

1. Dairi
2. Nias
3. South Tapanuli