Sgt Bowe Bergdahl, who went missing from his US Army base in Afghanistan in 2009, is to be charged with desertion, US officials say.
The US Army will make a formal announcement at Fort Bragg, North Carolina at 15:30 local time (19:30 GMT).
Sgt Bergdahl was freed in May after five years of captivity by the Taliban.
His release – the product of a controversial prisoner swap – sparked a heated political row.
US Army officials told the BBC that a “lengthy statement” will be read this afternoon at the base of US Army Forces Command in North Carolina.
Sgt Bergdahl will also be charged with misbehaviour before the enemy, anonymous officials told the Associated Press news agency.
His release enraged Republicans, who said that the prisoner swap – which freed five Guantanamo Bay detainees – could ultimately put American lives at risk.
Top Congressional Republicans argued the deal violated US law and amounted to negotiating with terrorists – accusations denied by the Obama administration.
Fellow soldiers said Sgt Bergdahl knowingly wandered away from his unit while deployed in Afghanistan in June 2009.