Los Angeles- Actor Brad Renfro pleaded guilty Thursday to drug charges resulting from his arrest in a downtown sting just before Christmas, and the judge said he would sentence him to three years’ probation.

The sentence would be lighter than Renfro had predicted after he was arrested Dec. 22.

“I am going to prison,” he told detectives who escorted him into an alley for processing after the bust at 6th and Spring streets. A Times reporter was present at the time.

After his arrest, the star of such movies as “Apt Pupil” and “The Client” entered a live-in drug rehabilitation program, where he stayed for about a month, said his attorney, Richard Kaplan.

“He is still in the program, but it is no longer residential,” Kaplan said.

Renfro pleaded guilty Thursday to attempted possession of heroin. Under Proposition 36, which provides many drug offenders the option of entering rehabilitation rather than prison, he will be assessed at a hearing March 6, Kaplan said.

Judge David Horwitz is to formally sentence Renfro at that time.

Renfro, 23, is seeking outpatient treatment so he can continue acting.

Renfro was among 14 people arrested in a crackdown intended to dissuade outsiders from coming to skid row to buy narcotics.

The actor faces up to 18 months in prison if he violates his probation. In 2002 he entered rehabilitation after being booked on suspicion of driving without a license and public intoxication. In Florida in 2001, he was charged with taking a yacht not belonging to him for a joy ride.