FARGO (AP) - A teenager accused of killing his sister is scheduled to enter a plea in Fargo instead of going to trial in Bismarck, prosecutors announced the day before his trial was to start.

Sixteen-year-old Sergei Carlson of Sun Prairie, Wis., is charged with murder and a deviate sexual act in the July 2007 death of his 16-year-old sister, Whitney, in her Fargo home.

Judge John Irby had twice rejected a plea agreement, and jury selection was to start today in Bismarck. But a statement issued Sunday afternoon by Cass County State's Attorney Birch Burdick said the trial was off, and that Carlson would enter a plea this morning in Fargo instead.

Carlson is expected to change his plea to guilty without the agreement reached by attorneys earlier and rejected by Irby. That agreement had called for a 30-year prison sentence.

Burdick' statement said those involved "do not anticipate further comment on this matter until tomorrow's hearing." He said the hearing was tentatively set for 10 a.m., with the time depending on the availability of a courtroom.

Officials said Sergei Carlson told police he strangled his sister in her bedroom with his hands on July 13, 2007, put pillows over her face to muffle her sounds, then had sexual contact with her.

Whitney's mother, Penny Ripplinger, found her lying in bed with blood on her face the next morning and called authorities.

Authorities said that when police arrived, Sergei Carlson had duct tape on his shorts and a blood spot on his shirt that DNA testing would later show belonged to his sister.

Sergei Carlson, who was 15 at the time, originally was charged as a juvenile. Because of his age and the severity of the charges, the case was moved to adult court, where the charge carries a maximum sentence of life in prison.

In rejecting the earlier plea agreement, Irby said it failed to adequately address the issue of rehabilitation and civil commitment.

Sergei Carlson was adopted from Russia when he was 7 years old and moved with his father, the Rev. Scott Carlson, to Wisconsin in 2002. Whitney Carlson lived with her mother in Fargo.