The Basque (search) separatist group ETA (search) may call a unilateral cease-fire in its campaign of violence, a founder and other Basque sources said, in an effort to win political concessions from the newly elected Socialists due to take power next month.

Julen Madariaga, a founding member of ETA, said he thought a truce could be called soon.

"I have the impression that in a very short time -- in coming days, or coming weeks -- that ETA will declare a cease-fire," he said in a telephone interview Monday night from his home in southern France.

Within the month, Jose Luis Rodriguez Zapatero (search) and his Socialists are to take over from the conservative Prime Minister Jose Maria Aznar (search), who cracked down on ETA.

"ETA always has known how to take advantage of these occasions. ... It's very weak and needs a strategic truce," said Kepa Aulestia, a Basque writer who focuses on ETA issues in his columns in El Correo and La Vanguardia newspapers.

ETA issued a statement Sunday proposing dialogue with the Socialists, but Zapatero responded the following day with these point-blank words: "The only communique I await from ETA, as do the vast majority of Spaniards, is one in which it abandons violence."

Aznar's Popular Party government had succeeded in weakening ETA, but has not been able to end the separatist group's violence, which has killed more than 800 people since the late 1960s.

Spanish and French police arrested more than 150 suspected ETA members last year, including senior commando leaders, and the number of killings blamed on ETA dropped to three, compared with 23 in 2000 after the last cease-fire ended.

The government had claimed ETA used that previous truce to regroup, and 2000 was its deadliest year in almost a decade.

Politicians and analysts in northern Spain said they expected a new ETA cease-fire.

"I believe there will be a truce soon," said Gorka Espiau of the Elkarri movement, which advocates dialogue with ETA.

ETA, whose name is the Basque-language acronym for Basque Homeland and Freedom, demands independence for the three Basque country provinces and part of neighboring Navarra in northern Spain, and three other areas in southwest France on the other side of the Pyrenees mountain border.

A minority of Basque nationalists support that demand -- if not ETA's bombing campaign. Others want more autonomy, but not necessarily outright independence. About half of the region's 2 million people want to remain part of Spain.

The three-province Basque country is one of 17 autonomous regions created by the 1978 constitution that followed the death of longtime dictator Gen. Francisco Franco.

The region already collects and spends its own taxes and manages many of its public services. If it gets more rights, or independence, there are likely to be more demands from other regions, notably Catalonia in the northeast, which have their own languages, cultures and autonomy aspirations.

"The Basques have an outrageously good deal right now," Charles Powell, historian at San Pablo University-CEU, said in a recent interview. Any additional concession "would set a trend in motion that would be very difficult to stop. For me, this is the area of greatest uncertainty right now."

Police recently foiled two bombing attempts blamed on ETA, including one on trains headed to downtown Madrid on Christmas Eve. A half-ton bomb was found in late February in a truck apparently headed for Madrid.

The Aznar government originally blamed ETA for the March 11 railway bombings in Madrid, which killed 190 people and wounded more than 1,800. But investigators are now focusing on an Islamic group with alleged ties to Al Qaeda.