Army Sgt. Bowe Bergdahl of Hailey appeared before a military judge and pleaded guilty to desertion and misbehavior before the enemy.
His lawyer says the prosecution and defense have not agreed to a stipulation of facts in the case, which is an indication that they did not reach a deal to limit his punishment.
Bergdahl is charged with endangering his comrades by walking away from a remote post in Afghanistan in 2009.
The misbehavior charge carries a maximum penalty of life in prison, while the desertion charge is punishable by up to five years.
Sentencing for the soldier, who was held by the Taliban and its allies for five years, is expected to take place later in October.