The plea deal by Staff Sgt. Robert Bales must be approved by a judge and a commanding general, the soldier’s lawyer John Henry Browne told CNN.
In addition to those killed, six Afghans were wounded in the March 2012 attack near a small US base in Afghanistan’s Kandahar province.
The US Army did not comment on any potential deal, CNN said.
A hearing in the case is scheduled for June 5.
Bales’ attorneys said the soldier 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 PTSD (post-traumatic stress disorder) and a concussive head injury,” Browne said earlier.
Afghan authorities have called for swift action in the case.
“He committed a mass killing crime, and we would like the court in the US to implement justice and punish him according to the crime,” Ahmad Zia Syamak, spokesman for Afghan President Hamid Karzai, told CNN.—IANS.