A key crossing point between one-time bitter enemies Ethiopia and Eritrea is set to reopen after a border war shut it in 1998.
The border post, just north of the Ethiopian town of Zalambessa, is on the main road linking the two countries.
Prime Minister Abiy Ahmed of Ethiopia and President Isaias Afewerki of Eritrea are there to witness the reopening, which is part of their ongoing rapprochement.
It follows a peace deal in July restoring diplomatic and trade relations.
The reopening coincides with the Ethiopian New Year, adding to the festive atmosphere.
The war, fought over the exact location of the boundary between Ethiopia and Eritrea, began in May 1998 and left more than 70,000 people dead.
It ended in 2000 with the signing of the Algiers agreement. But peace was never fully restored as Ethiopia refused to implement a ruling by a border commission established by the agreement.