WASHINGTON (CNN) -- Audio of Pfc. Bradley Manning telling a military court that he provided classified information to the WikiLeaks website has been posted on the Internet by the Freedom of the Press Foundation.
"This marks the first time the American public has heard the actual voice of Manning," the group said in a statement Monday.
Access to the military court proceedings for Manning is limited, and observers are not allowed to use recording devices. The foundation did not say how it obtained the audio but complained that the proceedings should be available to the public.
"By releasing this audio recording, we wish to make sure that the voice of this generation's most prolific whistle-blower can be heard -- literally -- by the world," said the group's statement.
The military does not view Manning, 25, as a whistle-blower. It alleges he is responsible for the largest leak of classified documents in U.S. history.
On February 28 he pleaded guilty to 10 of the 22 charges against him and faces up to two decades in jail. In that proceeding, Manning spent more than an hour reading a statement explaining his actions. He said he passed on information that "upset" or "disturbed" him but didn't give Wikileaks anything he thought would harm the United States if it were made public.
In the audio released by the foundation, Manning reads in an unrushed manner.
"Manning's actions should be seen as an overdue sliver of sunlight into an overly secret system rather than as a basis for prosecution seeking decades of imprisonment," the group said in its statement.
The Army released a statement saying it has informed the military judge in Manning's case that the rules of the court were violated. "The U.S. Army is currently reviewing the procedures set in place to safeguard the security and integrity of the legal proceedings, and ensure Pfc. Manning receives a fair and impartial trial," the Army said.
The U.S. military first detained Manning in May 2010 for allegedly leaking U.S. combat video -- including a U.S. helicopter gunship attack posted on WikiLeaks -- and classified State Department cables.
In this statement to the court, Manning said he initially contacted the Washington Post and the New York Times to provide information. Manning said he either wasn't taken seriously or ended up just getting voice mail, so he gave the information to WikiLeaks.
"I believed if the public was aware of the data, it would start a public debate of the wars," Manning told the court.
Manning did not plead guilty to the most serious charges against him, including violating the Espionage Act and aiding the United States' enemies. Manning's court-martial on those charges is scheduled to begin June 3.