The Basque separatist group ETA, which has waged a decades-long campaign for independence, plans to fully lay down its weapons by April 8, the head of the regional Basque government, Inigo Urkullu, said Friday.
He asked French and Spanish governments to help facilitate talks with the group, which has said it will give up its arms for amnesties or improved jail terms for imprisoned members.
But the central government in Madrid, a fierce opponent of ETA, reacted with scorn, demanding that the group simply "dissolve" and never reappear.
Urkullu confirmed the possibility that ETA was ready to give up its arms after decades of conflict in Spain and France, and said he hoped it would be "definitive, unilateral, irrevocable, complete and legal".
"The Basque government judges credible the potential for a final disarmament in the short term," Urkullu said.
"It asks... the Spanish and French governments to show ambitious vision and open direct lines of communication" in order to reach "a goal with historic importance for our society."
ETA, founded in 1959 and considered a terrorist group by the European Union, has been seeking to negotiate its dissolution in exchange for amnesties or improved prison conditions for its roughly 350 members held in Spain and France.
The group is blamed for the deaths of 829 people in a four-decade campaign of bombings and shootings for an independent Basque homeland, which straddles northern Spain and southwestern France.
But Prime Minister Mariano Rajoy bluntly said disarmament should be unilateral, and ETA should then consign itself to oblivion.
Speaking at a regional conference of his conservative party in Madrid, Rajoy said: "ETA has decided to unilaterally disarm. May it do so, and while it's about it, may it dissolve itself."
Ruling out any special treatment for ETA, he said: "The Spanish government will apply the law equally to everyone."
Interior Minister Juan Ignacio Zoido reiterated the tough line.
"What ETA must do is dissolve itself and disappear," he wrote on Twitter.
"It has had time to disarm and it must know that it won't get anything in exchange."
Earlier Friday, an activist in Bizi, a Basque association, told French daily Le Monde that the group's disarmament should be completed if possible before France's upcoming presidential election, whose first round of voting is set for April 23.
"ETA has given us the responsibility of disarming its arsenal and, on the evening of April 8, ETA will be completely disarmed," said the activist, Txetx Etcheverry.
Arnaldo Otegi, spokesman for the pro-independence party Sortu, which counts old ETA members among its elected leaders, echoed Urkullu's statements.
"We hope that, this time, the process for disarming will be absolute and that this time it will be complete, that it will go all the way and to its ultimate consequences," he said.
- Recent arrests weakened ETA -
Its last deadly attack was in 2010, when a policeman was killed during a shootout with ETA militants in a Paris suburb.
It declared a ceasefire in October 2011 but has refused to give up its weapons.
But a source later confirmed to AFP that "ETA will take steps to make this happen" before April 8.
Both France and Spain have long refused direct negotiations with the group, demanding its complete dissolution with nothing in return.
The separatist group has been severely weakened in recent years after hundreds of its members were arrested and some of its weapons were seized.
In November, the most senior ETA leader still at large, Mikel Irastorza, was arrested after a raid on a home in southwest France.
Earlier this month, Spain's Guardia Civil police force discovered seven drums of explosives in a rural area near the town of Irun on the border with France, which they suspect belonged to ETA.