Spain's prime minister says he will announce in June the start of direct talks with the armed Basque separatist group Eta.
Mr Zapatero is to announce the start of the process of dialogue
Jose Luis Rodriguez Zapatero said he would go to parliament to announce "the start of the process of dialogue to achieve the end of violence with Eta."
Eta declared a permanent ceasefire on 22 March. It has been engaged in an armed campaign for more than 30 years.
Mr Zapatero was speaking at a Socialist party meeting in the Basque region.
He said: "Just as I announced, next month I will communicate to the political forces the start of the process of dialogue to achieve the end of violence with Eta."
In April, Mr Zapatero discussed the ceasefire with Basque leader Juan Jose Ibarretxe.
Eta declared a permanent ceasefire on 22 March
The two men said Eta must stop using extortion against businesses and politicians.
Mr Zapatero said multi-party talks on the political future of the Basque region could only begin once the Eta ceasefire was confirmed.
His deputy, Maria Teresa Fernandez de la Vega, said Eta's banned political wing Batasuna would be excluded from such talks.
The BBC's Danny Wood, in Madrid, says the prime minister's latest announcement of the start of a peace process shows that the government is confident that this ceasefire is permanent.
But the Spanish public is not so sure.
A recent poll conducted by a government-financed agency suggested that most Spaniards were sceptical of the Eta ceasefire.
A total of 53.9% of those questioned said they were doubtful of Eta's intentions, while 43.1% said their reaction to the truce was one of hope, Centre for Sociological Research survey said.
On Friday, meanwhile, reports quoted Arnaldo Otegi, leader of Batasuna, as saying the peace process was in a moment of "extreme gravity".