America's top military official is accusing the WikiLeaks website of giving the country's enemies "valuable information."
Joint Chiefs of Staff Chairman Admiral Mike Mullen issued the criticism late Saturday in a post on Twitter.
Mullen also called the release of nearly 400,000 classified U.S. military documents from the Iraq war "irresponsible."
The founder of WikiLeaks defended the release at a news conference in London Saturday. Julian Assange, said the decision to release the documents "is about the truth" and that the documents contain no names or information harmful to any group or individual.
Among the revelations, the documents indicate more than 100,000 people were killed following the U.S.-led invasion in 2003, and that more than 60 percent of them were civilians. They also report 15,000 unknown or unreported deaths.
In an e-mail to reporters Friday, U.S. Defense Department spokesman Geoff Morrell called the documents "snapshots of events" that "do not tell the whole story."
The U.S. military has also said the publication of the files could endanger the lives of American troops and their Iraqi allies.
The files contain raw accounts from the battlefield, including incidents in which American soldiers killed civilians at checkpoints, or fired on insurgents who had tried to surrender.
In one case reported in The New York Times, one of four media outlets given advance access to the documents, U.S. soldiers shot and killed their own interpreter after mistaking him for a militant.
The new documents also exhibit cases in which Iraqi forces abused Iraqi detainees. The files indicate that while American forces informed Iraqi officials of the problems, they took no direct action to stop the abuse.
There are also reports revealing Iran's role in the war, such as incidents in which detainees spoke of having Iranian help, and the discovery of Iranian-supplied weapons.
Earlier this year, WikiLeaks published some 77,000 secret documents relating to the war in Afghanistan, including the names of Afghan informants.
WikiLeaks has not identified the source of the documents but suspicion has fallen on an Army intelligence analyst, Bradley Manning, who is currently in military custody. He was arrested earlier this year for allegedly leaking a 2007 video of a helicopter strike in Iraq that killed two Iraqis on assignment for the Reuters news agency.
Some information for this report was provided by AFP.