The US said he was suspected of downloading from SIPR Net.
He reportedly then passed on the data, including army videos and diplomatic messages, to the WikiLeaks website.
WikiLeaks has repeatedly said it does not have the confidential messages and the site itself is not mentioned in the charges against Private First Class (Pfc) Manning.
A former hacker, Adrian Lamo, reported Pfc Manning to the US authorities. He said the intelligence analyst admitted, in a series of online chats, to sending data to the whistle-blowing website.
In the redacted charge sheet detailing the accusations against Pfc Manning, the Army alleges that he transmitted, "to a person not authorised to receive it", a classified US Department of State cable described as "Reykjavik 13".
The US also alleges Pfc Manning obtained 150,000 US diplomatic cables without proper authorisation.
- BBC Inputs.