A former Salvadoran army intelligence agent and self-professed member of the First Brigade "death squads" was sentenced in federal court yesterday to six months in jail for illegally reentering the United States six years after he was deported.

Cesar Vielman Joya-Martinez, 28, convicted last September in U.S. District Court in Alexandria, was arrested last spring and charged with illegal reentry after he appeared at the Immigration and Naturalization Service offices in Arlington and applied for political asylum.

The United States has begun deportation proceedings against Joya-Martinez, and the Salvadoran government has asked that he be extradited to that country to face possible criminal charges.

Daniel Alcorn, Joya-Martinez's attorney, bridled yesterday when Assistant U.S. Attorney Jan Reincke asked U.S. District Judge Claude M. Hilton for a stiff prison sentence in part because Joya-Martinez has admitted killing several people while he was with the Salvadoran army's First Brigade.

Alcorn argued Joya-Martinez should be credited for "his efforts to try to put a stop to some of these activities" by offering information about the death squads.

"He has offered to cooperate with the U.S. government, and they have shown no interest whatsoever," Alcorn said in an interview yesterday.

Recent news reports have quoted an unnamed Bush administration source as saying the United States has tried to conceal information involving the killing of six Jesuit priests in El Salvador in November 1989. Alcorn said Joya-Martinez left El Salvador before the killings but is well acquainted with a Salvadoran colonel who is one of eight soldiers charged in the incident.