Pfc Bradley Manning, 22, has been charged with eight federal criminal law violations including one count of transmitting classified information to an unauthorised third party, in violation of the Espionage Act.
Pfc Manning, from Potomac, Maryland, is suspected of leaking a classified 2007 video of an Apache helicopter strike that killed 12 civilians in Iraq, including two journalists from the Reuters news service. The charges also accuse him of obtaining more than 150,000 diplomatic cables and a classified presentation.
The soldier, who was deployed with the 2nd Brigade, 10th Mountain Division, in Baghdad, was arrested in Iraq in May and transferred to a US military detention unit in Kuwait after reportedly "confessing" to a computer hacker in California on a chatline.
Footage of the helicopter assault on a Baghdad square in 2007 was published on in the WikiLeakswebsite in April in defiance of the Pentagon.
It included a transcript of the crews of helicopters seeking permission to open fire, with members of the crew hoarding saying "Come on, let us fire" as well as "light 'em up!" and "keep shooting, keep shooting".