US army private Bradley Manning returned to a military courtroom in Maryland on Wednesday to seek the dismissal of 10 of the 22 charges he faces over the biggest leak of government secrets in US history.
The intelligence analyst is charged with aiding the enemy by causing hundreds of thousands of classified war logs and diplomatic cables to be published on the WikiLeaks website in 2009 and 2010.
The defence told a military judge at the pretrial hearing at Fort Meade that the US government used unconstitutionally vague language in eight counts charging Mr Manning with unauthorised possession and disclosure of classified information.
They said that two other counts falsely allege he lacked authorisation to access computers linked to a Defence Department network used for classified information.
Mr Manning's military trial is due to begin on September 21.
He is likely to spend the rest of his life behind bars if found guilty.