One of several men accused of assassinating former Chilean ambassador Orlando Letelier in a 1976 car bombing pleaded guilty in federal court yesterday to conspiring to murder a foreign official.

Jose Dionisio Suarez Esquivel was arrested in April in St. Petersburg, Fla., after a 12-year search. Last May, he pleaded not guilty to conspiring to assassinate Letelier.

Letelier and his secretary, Ronni Moffitt, were killed Sept. 21, 1976, by a car bomb that was set off by remote control as they drove around Sheridan Circle. Moffitt's husband, Michael, who was sitting in the back seat, was not seriously injured.

The bombing later was linked to the Chilean secret police, known as DINA, and was seen as an attempt to silence Letelier, who had been an outspoken critic of the Chilean military regime headed by Gen. Augusto Pinochet.

Letelier had served as Chile's ambassador to the United States under President Salvador Allende, who was ousted in 1973 in a coup led by Pinochet.

At the time of his death, Letelier worked for the Institute for Policy Studies, a liberal think tank that opposed U.S. intervention in Chile.

Under the terms of Suarez's plea, the government agreed to press for a sentence of no more than 12 years for Suarez, who could have been sentenced to life imprisonment if convicted.

Prosecutors also agreed not to prosecute Suarez's wife, Elizabeth, for hiding her husband after the bombing.

One of Suarez's lawyers, Paul Goldberger, told reporters after yesterday's hearing before Chief U.S. District Judge Aubrey Robinson that his client's main reason for agreeing to plead guilty was the protection it afforded his wife.

"His primary concern all along has been the potential prosecution of his wife," Goldberger said.

At a news conference after the plea agreement was announced, U.S. Attorney Jay B. Stephens said that Suarez has been held accountable for the assassination and likely will serve more time than any of the other defendants in the case.

The two others indicted but not arrested in the case are Juan Manuel Contreras Sepulveda and Pedro Espinosa Bravo, both of whom are in Chile.

An American agent for DINA, Michael Townley, identified as the person who actually placed the bomb, pleaded guilty in 1978 to conspiring to assassinate Letelier.

At yesterday's news conference, Stephens was asked whether he settled for too little given the seriousness of the case, in which five counts, each carrying a possible life sentence, were dropped in exchange for a maximum 12-year sentence.

"We believe this is a substantial disposition in this case," Stephens said. "Mr. Suarez faces up to 12 years in prison, which is more time than any other defendent has served in this case."

Stephens said the investigation remains open until the remaining three men are brought to justice.

Staff writer Carlos Sanchez contributed to this report.