Jose Luis Rodriguez Zapatero, Spain's prime minister, told parliament on Thursday that the government would begin a dialogue with Eta, although he said the country's democracy "would not pay any political price to achieve peace".
"The process is going to be long, tough and difficult," he said.
"We'll handle it with determination and prudence, with unity and loyalty and always with respect to the memory of the victims."
Zapatero gave no details of where or when talks would take place, saying that Alfredo Perez Rubalcaba, the interior minister, would update other political parties on the progress of talks in September after parliament's summer break.
Eta announced a permanent ceasefire in March after more than 30 years of armed struggle for independence for the northern Basque region. About 850 people were killed in the violence.
Zapatero had said Eta must declare a ceasefire before talks on the political future of the Basque region could begin.
But the Spanish government's decision to hold talks with Eta has angered some Spanish politicians, and the country's main opposition right-wing Popular Party said on Thursday it would not support a peace process involving talks with Eta's political wing, the banned Batasuna party.
Spaniards protested against
talks with Eta in June
Party leader, Mariano Rajoy, said: "We cannot give our support to the government in this process. It's not acceptable to talk to Batasuna because it would be like talking with terrorists."
About 200,000 people marched through the streets of Madrid this month, demanding that the government call off talks with the group.
The march was called by the Popular Party and victims' groups.