A US Army psychiatrist charged for the deadly 2009 mass shooting on a US army installation will not be allowed to plead guilty to any charges, a military judge has ruled.

Major Nidal Hasan, 40, charged with 13 counts of premeditated murder and 32 counts of attempted premeditated murder, faces the death penalty if convicted.

Col Tara Osborn yesterday ruled that pre-trial publicity around the case would not unfairly prejudice a jury and set the start of jury selection for May 29.Testimony is scheduled to begin on July 1.

Hasan's attorneys previously said he was ready to plead guilty to the 13 counts of premeditated murder he faces in the worst mass shooting on a US military installation, but Army rules prohibit a judge from accepting a guilty plea to charges that carry the death penalty.

According to military law, however, he cannot plead guilty because it is a death  Defence attorneys then asked that Hasan be allowed to plead guilty to 13 counts of unpremeditated murder, which does not carry the death penalty.

No guilty pleas would have stopped his murder trial or possibility of being sentenced to death.

But the judge ruled Hasan cannot plead guilty to those lesser charges or the 32 counts of attempted premeditated murder that he also faces.

He still would have been tried on the premeditated murder charges, so pleading guilty to the attempted premeditated murder charges could have been used against him at trial, Osborn said.

She also said he would not be allowed to plead guilty to unpremeditated murder and unpremeditated attempted murder, because that "would be the functional equivalent of pleading guilty to a capital offence."

A US-born citizen of Palestinian descent, Hasan was a licensed psychiatrist who joined the Army in 1997.

He had been scheduled to deploy to Afghanistan before the killings, but had been telling his family since 2001 that he wanted to get out of the military.

Hasan had told his family he had been taunted after the terrorist attacks of September 11, 2001.