Gates: WikiLeaks didn't reveal intel sources

WikiLeaks's publication of 70,000 classified military documents in July did not out any critical sources of intelligence in Afghanistan, according to a letter from Defense Secretary Robert Gates.

In a letter to Senate Armed Services Committee chairman Carl Levin (D-Mich.) dated Aug. 16 and obtained by CNN, Gates asserts that while the online whistleblower's publication of the documents did pose a risk to national security, it did not compromise any key sources of intel. Gates said most of the information published related to "tactical military operations."

"The initial assessment in no way discounts the risk to national security," Gates wrote. "However, the review to date has not revealed any sensitive intelligence sources and methods compromised by the disclosure."

Gates said the documents did contain the names of some Afghans who cooperate with the United States and could potentially face reprisal from the Taliban, but a NATO official told CNN there hasn't been any instances of Afghans needing protection or having to be moved because of the leak.

Gates also said the Pentagon still views the leak as likely to cause significant harm to U.S. national security and said the military is working closely with its allies to mitigate the damage. He also said there is the possibility of more documents being published, a possibility for which the Pentagon is bracing itself. Military officials are holding Army Pfc. Bradley Manning in Quantico on suspicion he leaked the documents to WikiLeaks.

WikiLeaks founder Julian Assange has said the site is in possession of more than 15,000 additional documents on the Afghan war it is planning to publish after redacting for names and other sensitive information. WikiLeaks is also expected to publish about 400,000 documents from the Iraq war as early as next week.