ETA prisoners will begin in the coming days to formally ask the government to consider granting inmates lighter sentences and other benefits, as well as freeing those who are sick.
The ETA prisoners group EPK also made a call to inmates to vote in Sunday's election, which they called a race of "special importance."
In a statement published Sunday in the pro-Basque independence newspaper Gara, ETA said that it will support all of the prisoners' requests.
The government and the High Court have ruled out a general amnesty for inmates and said that they will deal with any requests on a case-by-case basis, as they would do with any other prisoner.
ETA also wants the government to consider granting some inmates parole.