PROVIDENCE — Mobster Anthony M. “The Saint” St. Laurent Sr. has been indicted on federal charges in a plot to kill another high-ranking member of the Patriarca crime family.

A grand jury indicted St. Laurent on Wednesday for solicitation to commit a crime of violence and murder for hire. The authorities say the intended target was Robert P. “Bobby” DeLuca Sr., a capo regime in the mob, who spent more than 10 years in federal prison for extortion.

St. Laurent, serving a five-year term at Federal Medical Center Devens, in western Massachusetts, for extortion, will appear before a judge via a videoconference on April 20 to face the new charges.

If convicted, St. Laurent could spend the rest of his life in prison.

Prior to the indictment, there had been discussions between St. Laurent and federal authorities on a possible plea agreement in the case. At that point, he had been charged in a federal affidavit of solicitation to commit murder for hire with DeLuca as the target.

Since the mid-1990s, DeLuca has accused St. Laurent of being an informant for the Rhode Island State Police and the FBI, a charge that St. Laurent has denied. The alleged murder-for-hire plot dates to 2006, when St. Laurent was running an extortion ring from his house at 2 Rotary Drive in Johnston.

DeLuca works in the kitchen of Sidebar, a downtown bar and restaurant that is owned by Artin H. Coloian, a lawyer and onetime top aide in the administration of former Mayor Vincent A. Cianci Jr.