"The peace negotiation that will be held with (the Oromo Liberation Army) will start the day after tomorrow in Tanzania," Abiy said.

"The Ethiopian government and people will need this negotiation very much.

"I call upon everybody to play (their) part."

The "official" OLA has been fighting the Ethiopian federal government since it split in 2018 with the historic Oromo Liberation Front (OLF) when it renounced armed struggle.

Abiy spoke at a gathering of parties to the Tigray peace process which saw a deal on November 2 end a two-year conflict between the federal government and rebelling regional authorities.

He gave no further details on the format of the new talks, who would mediate or where they would be held. OLA spokesman Odaa Tarbii did not respond immediately to an AFP request for comment.

The split of the Oromia rebel groups gave rise to a string of armed groups claiming to be one, but with loose ties.

The OLA's strength, estimated at a few thousand men in 2018, has increased significantly in recent years, though observers believe it is insufficiently organised or well-armed to pose a real threat to the federal government.

Oromia has suffered ethnic massacres in recent years carried out by unknown groups.

The OLA has been repeatedly accused by Abiy's government of being responsible for these massacres, which it denies.

The government is accused of waging an indiscriminate crackdown that has fuelled Oromo resentment against the central government.