By Karen Brooks

FORT HOOD, Texas (Reuters) - The Army psychiatrist accused of killing 13 people at Fort Hood is expected to give details on Wednesday about his legal defense which is based on his wish to protect Afghanistan and the Taliban leadership, according to a statement from the U.S. military post.

Colonel Tara Osborn, the military judge overseeing Army Major Nidal Hasan's capital murder court martial, instructed him to develop his defense case for trial and present it to the court on Wednesday.

Hasan, a U.S.-born Muslim, has asked for a three-month delay of the trial, saying he needed time to prepare his defense after the judge ruled he could represent himself. Osborn is expected to rule on the request for the delay at the Wednesday hearing.

The Army psychiatrist, 42, stands accused of killing 13 and wounding 32 others when he opened fire at the Texas military base on November 5, 2009. He could face the death penalty if convicted.

"His defense is based on his desire to protect the Islamic Emirate of Afghanistan and the leadership of the Taliban to include Mullah Mohammad Omar," the Fort Hood press release said.

Jury selection in the trial had originally been set for Wednesday. The judge said on Tuesday that the more than 50 potential panelists would be due in court no earlier than Monday. The trial is set to begin July 1.

Legal experts said the purpose of the hearing is for Hasan to present the legal foundation for his argument that had he not killed and wounded U.S. military personnel at the base they would have been deployed to the Middle East to kill Muslims.

For Hasan to argue that he was protecting Muslims, there would have to be an imminent and immediate threat to them, said Jeffrey Addicott, a former legal adviser to the Army Special Forces and director of the Center for Terrorism Law at St. Mary's University School of Law in San Antonio.

"There is no immediate threat when the people you kill are here in the United States," said Addicott.

(Additional reporting by Jim Forsyth; Editing by Corrie MacLaggan and Andrew Hay)