Story highlights Shooting spree strained already tense U.S.-Afghan relations

Army Staff Sgt. Robert Bales hopes to avoid the death penalty

He is accused of killing 16 and wounding six Afghans

Attorneys have said he suffers from post-traumatic stress disorder

In order to avoid the death penalty , U.S. Army Staff Sgt. Robert Bales intends to plead guilty in the killing of 16 Afghan villagers, his lawyer said Wednesday.

A plea deal -- which Bales' lawyer John Henry Browne told CNN about by text message, as he was meeting with his client -- must be approved by a judge and a commanding general.

In addition to those killed, six Afghans were wounded in the March 2012 attack near a small U.S. base in Afghanistan's Kandahar province.

The shooting spree strained already tense U.S.-Afghan relations and intensified a debate about whether to pull out American troops ahead of their planned 2014 withdrawal.

The Army would not comment on any potential deal Wednesday. A hearing in the case is scheduled for June 5.

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Bales' attorneys have said that he suffers from post-traumatic stress disorder and sustained a traumatic brain injury during a prior deployment to Iraq.

"We think the Army is attempting to escape responsibility for the decision to send Sgt. Bales to Afghanistan for his fourth deployment, knowing that he had (post-traumatic stress disorder) and a concussive head injury," Browne said last year.

"I think that the person who made the decision to send Sgt. Bales to the most dangerous area in Afghanistan in a small outpost is responsible for Sgt. Bales being in Afghanistan, and he should have never been there."

Afghan authorities have called for swift action in the case.

"He committed a mass killing crime, and we would like the court in the United States to implement justice and punish him according to the crime," said Ahmad Zia Syamak, spokesman for Afghan President Hamid Karzai.