Bergdahl, 29, was charged earlier this year with desertion and endangering US troops and could face the life sentence if convicted of the latter, more serious offence.

In ordering the court martial, Army General Robert Abrams did not follow the recommendation of a preliminary hearing which, according to Bergdahl's lawyer, called for Bergdahl to face a proceeding that could impose a potential maximum penalty of a year in confinement.

Bergdahl's lawyer, Eugene Fidell, said the defence team "had hoped the case would not go in this direction."

He also urged Republican presidential candidate Donald Trump, who has called Bergdahl a "dirty, rotten traitor," to "cease his prejudicial months-long campaign of defamation against our client."

Bergdahl disappeared on foot on June 30, 2009, from Combat Outpost Mest-Malak in Paktika Province, Afghanistan, and was subsequently captured by the Taliban.    

He left his post to draw attention to 'leadership failure' in his unit, Bergdahl said last week on the popular podcast Serial, which is foccusing a season on his case.

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