Pentagon is reviewing the classified documents to assess the damage caused by the leakage of voluminous intelligence materials running into more than 92,000 documents by a whistleblower site.
The classified documents on the war against terrorism in Afghanistan posted by WikiLeaks -- whose advance copies were made available to The New York Times, British daily Guardian and German weekly Der Spiegel.
The White House termed the postings as a breach of federal law.
Condemning the release of such classified documents, a Pentagon spokesman said it has taken the leak very seriously and was reviewing and assessing the damages these documents may have done to the defence forces.
"As they are made available, we will be looking at them to try to determine potential damage to lives of our service members and our coalition partners; whether they reveal sources in methods and any potential damage to national security," Marine Corps Col Dave Lapan, a Pentagon spokesman, told reporters.
"Since this was just released last night, we're still in the process going through that assessment," Lapan said.
Given that more than 92,000 documents were released, the spokesman said Pentagon would take weeks to make such determinations.
Pentagon has discovered early in the investigation is that the documents are classified at a 'secret' level, and not 'top-secret,' which is reserved for more sensitive material, he said.
"The disclosed documents reveal 'the type of reporting that goes on at the tactical level on a routine basis'. There's nothing we've seen so far that is particularly relevant," Lapan said.
The spokesman said Pentagon is concentrating on the information that has been made public, and is not investigating the source of the leak.
Pentagon regards Army intelligence analyst Bradley Manning as a possible suspect in the leaking of these classified documents, he said.
"He (Manning) is certainly one person that we would be looking at in terms of this leak. He's not the only person. We've neither ruled in or ruled out PFC Manning. We're still assessing the documents to see if we can determine the source of the leak," Lapan said.
Manning, 22, was arrested late May after he was turned in by a former hacker he befriended online. The army analyst is said to have established direct contacts with WikiLeaks founder Julian Assange.