The meeting will take place in Cambo-les-Bains in southwest France, where the separatist group is expected to make a historic declaration that it is ending its fight in Spain's Basque Country.
An international conference to support the peace process in the Basque region is to be held in France in early May, a mediator said on Monday, as separatist group ETA prepares to disband.
The meeting in Cambo-les-Bains in southwest France will take place on May 4 around the same time as ETA is expected to make a historic declaration that it is ending its fight in the Basque Country that straddles the border between Spain and France.
Civil society and political leaders are to be invited to the gathering at the former home of Edmond Rostand, the author of the famed play "Cyrano de Bergerac," mediator Raymond Kendall told a press conference.
The meeting would be "essential to advance the final peace process," he said in the French city of Bayonne.
ETA waged a nearly four-decade campaign of bombings and shootings for an independent Basque state.
It asked forgiveness from some of its victims for the first time on Friday in what was seen as a penultimate step towards disbandment, which is expected on the weekend of May 5-6.
Founded in 1959 at the height of Francisco Franco's dictatorship, ETA is blamed for the deaths of at least 829 people before it announced a permanent ceasefire in 2011.