Ryan Schallenberger's trial on federal explosives charges had been scheduled for March, but U.S. District Judge Bryan Harwell on Tuesday granted the request for more time from attorneys for the 19-year-old.
Prosecutors say the trial will take about a week. Harwell says he wants a statewide jury panel.
The teen was arrested in April 2008 after police say his parents picked up a package addressed to him containing ammonium nitrate.
Police found bomb-making materials and a tape Schallenberger wanted played after his death in an assault planned on Chesterfield High School.
Schallenberger has pleaded not guilty.