A former United States ambassador was sentenced Friday to 15 years of imprisonment after pleading guilty to charges that he served for decades as a secret agent for Cuba’s spy agency.

The Justice Department had described the acts of Manuel Rocha, 73, as one of the most serious, highest-reaching infiltrations of the U.S. government in history.

“Today’s plea and sentencing brings to an end more than four decades of betrayal and deceit by the defendant,” Assistant Attorney General Matthew G. Olsen said in a statement dated Friday.

The guilty plea and sentencing came after a year-long undercover operation in 2022 and 2023 conducted by an FBI agent posing as a Cuban spy. During that operation, the undercover agent secretly recorded Rocha detailing his own spy work and repeatedly referring to the United States as “the enemy,” according to the Justice Department.

Rocha told the FBI agent that his spy work was “more than a grand slam” and that he “strengthened the Revolution … immensely,” the Justice Department alleged. Prosecutors also said Rocha told the undercover FBI agent that Cuba’s General Directorate of Intelligence “asked me … to lead a normal life.”

After he entered a not-guilty plea, Rocha agreed to plead guilty in February to charges of conspiring to act as an agent of a foreign government. Prosecutors at the time dropped 13 other charges, including wire fraud and making false statements, the Associated Press reported. On Friday, Rocha also pleaded guilty to acting as an agent of a foreign government without notice.

The former State Department employee, who also served on the National Security Council and as U.S. ambassador to Bolivia, admitted to spying on the United States for more than 40 years, starting covert operations as early as 1973. Born in Colombia, Rocha became a naturalized U.S. citizen in 1978 and began ascending the ranks of the State Department in 1981, prosecutors said.

Over four decades, Rocha served at U.S. embassies in Argentina, the Dominican Republic, Honduras and Mexico. From mid-1994 to mid-1995, he worked on the National Security Council with a portfolio that included Cuba. He was sworn in as U.S. ambassador to Bolivia in July 2000, and in that job and others he gained access to national secrets, including classified information, which he allegedly shared with Cuban intelligence operatives.

Between 2006 and 2012, Rocha advised military officials at U.S. Southern Command, a military branch whose responsibility includes Cuba.

“To betray that trust by falsely pledging loyalty to the United States while serving a foreign power is a crime that will be met with the full force of the Justice Department,” Attorney General Merrick Garland told reporters when news of the accusations broke.

Prosecutors did not describe in the criminal complaint specific acts of espionage or how the FBI came to suspect him, but they said the agency received a tip about him before November 2022.

The undercover FBI agent told Rocha that they were a representative of a Cuban intelligence agency in Miami and that their mission was to “establish a new communication plan” with Rocha, who agreed to meet with the undercover agent.

During those meetings at an outdoor food court, the former ambassador allegedly said he created a public reputation as a “right wing person,” even as he was really committed to communist Cuba. He praised Fidel Castro and referred to other members of the Cuban intelligence agency as his comrades, prosecutors said.

After the year-long sting operation, Rocha was arrested in December. In addition to the prison sentence, the federal court ordered Rocha to pay $500,000, forfeit future pension payments, cooperate with the U.S. government and share details of his dealings with Cuba. Rocha also agreed in the plea agreement to work undercover for the U.S. government should agents request it.

“Rocha’s 15-year prison sentence, the maximum punishment for his crimes of conviction, sends a powerful message to those who are acting or seek to act unlawfully in the United States for a foreign government,” said Markenzy Lapointe, U.S. attorney for the Southern District of Florida.