Millionaire killer Robert Durst has been indicted on weapons charges in Louisiana, authorities announced Wednesday, indefinitely delaying his transfer to California to face a murder rap.

Authorities in New Orleans have been holding the eccentric real estate heir without bail since March 15, when he was arrested by two FBI agents who found a .38-caliber Smith & Wesson revolver and a bag of pot inside his room at the J.W. Marriott Hotel.

The agents had intended to serve a Los Angeles arrest warrant, where Durst is charged in the 2000 death of longtime friend Susan Berman, but arrested him separately for felony weapons possession.

If convicted, the 71-year-old tycoon would likely spend the rest of his life in a Louisiana prison.

“Durst lawyers want to get him to LA as quick as possible because they can beat that case,” said New Orleans criminal defense attorney Craig Mordock, who is observing the courtroom saga.

Mordock added that the New Orleans District Attorney’s Office may just want to nail Durst with something, rather than risk sending him to LA and watching him walk free.

“[The Los Angeles case] is a 15- year-old circumstantial case,” he said. “If he’s convicted [in New Orleans] on the felon-with-a-firearm charge, he is going to die in jail.”

Durst’s team of attorneys have been working to spring him from a New Orleans jail and have him extradited to Los Angeles to face murder charges, saying that his arrest for weapons possession was illegal because the FBI agents didn’t have a search warrant.

“The New Orleans case is a slam dunk,” said a law-enforcement source familiar with the case. “The LA case will be more challenging [for prosecutors] to prove.”

Berman was shot in the back of her head at her home in Beverly Hills, a day before she was due to be questioned by police who had reopened an investigation into the 1982 disappearance of the tycoon’s wife, Kathie Durst, in New York.

Durst appeared to make an unwitting confession to a number of killings during filming of the six-part HBO documentary “The Jinx: The Life and Deaths of Robert Durst.”