UNITED STATES (AFP) - US Army Sergeant Bowe Bergdahl, who was held by insurgents in Afghanistan for five years before being freed in a prisoner swap, appeared in court Tuesday (Dec 22) charged with desertion.

The 29-year-old soldier appeared before a military tribunal at Fort Bragg, North Carolina, to be formally arraigned on two charges. He did not enter a plea.

If convicted on a charge of desertion, Bergdahl could serve up to five years in prison, receive a dishonorable discharge, lose his rank and forfeit all pay.

But he also faces a second more serious charge, "misbehavior before the enemy," that could carry a life sentence.

Bergdahl, who was wearing his dark blue US Army dress uniform and medals, was briefed on his rights and replied with a soft "Yes sir" when asked whether he understood.

The hearing lasted 15 minutes and Bergdahl, who was represented by a military lawyer, asked to be represented by civilian counsel in future appearances.

Bergdahl deferred a decision on whether he would prefer to face court martial in front of a military judge or a panel of officers and fellow enlisted men.

The next hearing was scheduled for Jan 12.

Tuesday's public hearing was Bergdahl's first appearance before a judge since he disappeared from Combat Outpost Mest-Malak in Paktika Province, Afghanistan on June 20, 2009.

After departing the base, leaving behind his firearm, the young soldier was quickly captured by militants from the feared Haqqani faction, a Taliban-lined outfit blamed for many deadly attacks on US soldiers.

A search and rescue mission was launched and some of Bergdahl's former comrades have accused him of putting their lives in danger by his actions.

Nevertheless, the military worked hard to find him and he was eventually released to US special forces in May last year after the United States released five Afghan detainees from Guantanamo Bay.

Bergdahl was reassigned to administrative work at a US Army base in Texas but an investigation had been launched.

In March he was charged with "desertion with intent to shirk important or hazardous duty" and "misbehavior before the enemy by endangering the safety of a command, unit or place."

Bergdahl's lawyers have already protested that the charges go beyond what they see as the evidence against him and complained that remarks by Republican presidential frontrunner Donald Trump - who called Bergdahl a "dirty, rotten traitor" - may bias a jury.

For his part, the sergeant has told a Hollywood screenwriter researching for a movie that he walked off base in a bid to prove he was capable of solo heroics like fictional ex-CIA assassin Jason Bourne.

"I had this fantastic idea that I was going to prove to the world that I was the real thing, that I could be what it is that all those guys out there who go to the movies... want to be," Bergdahl told Mark Boal, in a call broadcast as part of investigative radio show "Serial." Bergdahl told Boal his original plan was to trek to another military base to draw attention to what he called a failure in leadership in his unit.

He wanted to create a manhunt that would scramble the military and the CIA so that, when he was found, he might be able to get the ear of a general.

But once off base, by his own account, Bergdahl realized he was in trouble.

He decided to appease the anger he would face by gathering intelligence and tried to track insurgents planting roadside bombs and return with useful information.

But he walked wildly off course and found himself in open desert with no cover when the sun came up.

He said he was spotted by six men armed with AK-47s and travelling on motorcycles.

The White House defended itself against the charges that it was wrong to free dangerous militants to secure Bergdahl's release by insisting no US service member is ever left behind.