Bradley Manning, the US Army private accused of passing military secrets to whistle-blowing site WikiLeaks, faces 22 new charges including the capital offence of 'aiding the enemy'.
According to a report by news agency Reuters, the charges are the result of a seven-month investigation into Manning, a former army intelligence analyst who served in Iraq.
Manning is accused of supplying WikiLeaks with information including the cache of 250,000 diplomatic cables released at the end of last year, and the earlier 'collateral murder' video documenting the killing of civilians by a US helicopter gunship, including two Reuters journalists.
The new indictments have been brought under the Uniform Code of Military Justice, and supplement the 12 charges laid against Manning last July.
New offences include 'wrongfully causing intelligence to be published on the Internet', violating army regulations on information security, and 'aiding the enemy' - a charge that carries a potential death sentence under military law.
Prosecutors maintain they will not seek the death penalty against 23-year-old Manning, but in a statement said: "If convicted of all charges, Manning would face a maximum punishment of... confinement for life."
US authorities are currently awaiting the findings of a panel looking into Manning's mental state. If the panel finds the private fit to stand trial, a grand jury may be convened.
Manning's mental health has been the subject of concern since he was taken into custody last May. In January, the soldier was placed on suicide watch, allegedly in breach of military regulations.
The incident follows allegations that Manning's treatment - which includes being confined to his cell for 23 hours a day and denied a pillow and bedsheets - amounts to torture.
Human rights campaign group Amnesty International recently labelled the conditions of Manning's detention "inhumane".
WikiLeaks founder Julian Assange has consistently denied any knowledge of Manning, but said that if the allegations against the private were true, he would be "an unparalleled hero".