The disclosure of classified reports about the Afghanistan war revealed tactics to the enemy and could endanger individuals who provided intelligence to the U.S. and its allies, Defense Secretary Robert M. Gates said Thursday.
Gates called the disclosure of the documents a "major security breach" and said "the battlefield consequences are potentially severe and dangerous." His statements were his first public comments since the anti-secrecy group WikiLeaks posted more than 70,000 war documents from 2004 to 2009 on its website Sunday.
A large-scale Pentagon effort is underway to review the voluminous files. Officials said they had already found documents that have the names of Afghans who supplied information to U.S. troops, though WikiLeaks founder Julian Assange has said the group withheld 15,000 documents to avoid identifying such individuals.
Assange has said his goal in releasing the documents was to focus attention on civilian casualties caused by the United States and its allies. The Pentagon, in arguing that the disclosures themselves could cause further casualties, was seeking to turn his reasoning against him.
"This is a huge amount of raw data," Gates said. "There is no accountability. There is no sense of responsibility. It is thrown out there."
It was not clear how many sensitive sources had been revealed. Gates and Adm. Michael G. Mullen, the chairman of the joint chiefs of staff who appeared with him, echoed comments by other senior officials who have asserted that the documents as a whole do not undermine what the Obama administration has been saying publicly about the war.
But the two Pentagon officials offered the most dire assessment to date of the possible consequences of the WikiLeaks disclosures, and they blamed Assange, a 39-year-old Australian, and WikiLeaks as much as the source of the documents for any potential damage.
"Mr. Assange can say whatever he likes about the greater good he thinks he and his source are doing, but the truth is they might already have on their hands the blood of some young soldier or that of an Afghan family," Mullen said.
Mullen did not answer a question about whether any retribution had occurred since the WikiLeaks disclosures.
Mullen's comments and others by Gates seemed to signal that the Pentagon plans an aggressive investigation that could go beyond merely prosecuting the leaker of the documents and that, at a minimum, the Pentagon aims to put WikiLeaks on the defensive.
WikiLeaks has declined to name its source, but the investigation is focused on Army Pfc. Bradley E. Manning, 22, an intelligence analyst who was charged in May with illegally downloading classified information, including a video of a U.S. attack in Iraq that later appeared on WikiLeaks.
Manning was stationed in Iraq but had access to the Afghanistan-related papers WikiLeaks has published, a U.S. official said. He is now in custody at a U.S. base in Kuwait.
Gates said he would not comment on an ongoing investigation.
Asked whether the Pentagon had contacted Assange about additional documents he may have, Gates said, "I'm not sure why we would. Do you think he would tell the truth?"
Gates said he had called FBI Director Robert Mueller on Wednesday to enlist his agency in the investigation, which is being led by the Army Criminal Investigation Command. "We will aggressively investigate and wherever possible prosecute" those responsible, Gates said.
Neither Mullen nor Gates made it clear what tactics or procedures might have been revealed that could cost soldiers' lives.
The documents present a ground-level look at U.S. Army tactics, including the use of surveillance drones, how units respond to Taliban attacks and other information that if closely studied might prove useful to an adversary.
Most of the units mentioned in the documents have rotated out of Afghanistan.