WASHINGTON (AFP) - The US soldier who was held by insurgents for five years after disappearing from his post in Afghanistan has been charged with desertion and "misbehaviour before the enemy", officials said Wednesday.

Sergeant Bowe Bergdahl, 28, was released in May last year in a swap for five Taleban detainees held at the US-run prison at Guantanamo Bay, Cuba.

The only American in uniform to be held by insurgents in the Afghanistan war, Bergdahl was held in captivity at the hands of Taleban-linked Haqqani insurgents after he went missing from his post in eastern Afghanistan near the Pakistani border in June 2009.

Army authorities plan to hold a news conference to discuss the charges against the former prisoner of war.

The desertion charge carries a potential death sentence, though legal experts say execution would be highly unlikely and a plea agreement could be reached before any trial goes ahead.

Some soldiers who served at the same eastern base have alleged that he walked out of his unit willingly, putting other troops at risk as they searched for him.

Their account has sparked outrage in some circles over the prisoner swap.

Bergdahl is being defended by a prominent lawyer and expert on military justice, Eugene Fidell, who teaches at Yale Law School.

Fidell, while declining to discuss the case in depth publicly, has said that Bergdahl was proud to wear the US uniform and has been made a scapegoat by people opposed to closing down the controversial prison camp in Guantanamo Bay, Cuba.