LOCKPORT – A North Tonawanda sex offender admitted in Niagara County Court Thursday that he violated his probation last month by having sexual contact with a 17-year-old boy.

At sentencing March 21, Robert W. Miller, 37, of Oliver Street, will receive no more than four years in prison and 10 years of post-release supervision. County Judge Matthew J. Murphy III said.

Miller also will have to plead guilty in North Tonawanda City Court to a sexual misconduct misdemeanor, Assistant District Attorney Robert A. Zucco said.

Miller was placed on probation in December 2009 after pleading guilty to first-degree sexual abuse for molesting a 14-year-old boy in North Tonawanda in 2008.