California officials on Tuesday postponed indefinitely the execution of a condemned killer, saying they would be unable to comply with a judge's order that a medical professional administer the lethal injection.

Prison officials called off the execution of Michael Morales, 46, after failing to find a doctor, nurse or other properly licensed person to deliver a lethal dose of barbiturate, said Vernell Crittendon, a spokesman for San Quentin State Prison. That mode of execution was settled on by prison officials after plans to kill Morales using a three-drug cocktail were delayed when two anesthesiologists refused to participate on ethical grounds.

Morales was initially scheduled to die at 12:01 a.m. Tuesday for torturing, raping and murdering a 17-year-old girl 25 years ago. The anesthesiologists were brought in because of a ruling last week by a federal judge considering whether the state's injection protocol might be unconstitutionally cruel and unusual. The doctors backed out after learning they might have to advise the executioner if the inmate woke up or appeared to suffer pain.

Prison officials then rescheduled the execution for Tuesday night, planning to skip the usual paralyzing and heart-stopping drugs and kill him with an overdose of a sedative. It wasn't immediately clear when the execution would be carried out, but it isn't likely to happen for months because of constitutional questions surrounding the mode of lethal injection in California.