A U.S. military judge ruled on Thursday that the trial for a military psychiatrist accused of killing 13 in a 2009 shooting spree at the U.S. Fort Hood Army base will be delayed until June.

Major Nidal Hasan's trial was scheduled to begin in March, but defense lawyers asked military judge Gregory Gross to delay the trial until July to allow more time to go through documents related to the case for key evidence needed for the trial.

Prosecutors argued that defense lawyers did not need more time, but Gross agreed to move the start date for the trial to June 12.

Hasan allegedly opened fire with two handguns on unarmed soldiers who were preparing for deployments to Iraq and Afghanistan at a crowded medical building at Fort Hood, Texas, on Nov. 5, 2009. The shooting rampage left 13 people dead and more than 30 others injured.

Hasan, 41, who was paralysed from the waist down after being shot by police the day of the rampage, has been in custody since the shooting. He has been charged with 13 counts of premeditated murder and 32 counts of attempted premeditated murder. If convicted, he faces the death penalty.