UPDATE: Wikileaks has lifted the embargo on its war documents, and details are starting to leak out. See the story from The Guardian for more information, which reveal serial detainee abuse, 15,000 unknown civilian deaths in war, and more.

WikiLeaks is set to release more than 400,000 Iraq war documents over the weekend, in what would be the biggest leak of classified documents in U.S. history, according to a Democracy Now report. The site's founder, Julian Assange, will provide more details at a Saturday morning press conference in London.

"Major WikiLeaks announcement in Europe at 10 a.m. tomorrow," Wikileaks tweeted on Friday.

Reports were circulating that the documents would be released Oct. 18, but WikiLeaks later dispelled those rumors via Twitter; Saturday's press conference wasn't confirmed until today.

WikiLeaks' Saturday release is expected to detail sensitive information such as "U.S. message traffic on tensions between Arabs and Kurds over contested boundaries, Iranian interference in Iraq, and killings of imprisoned Iraqis by their countrymen," said a Bloomberg report.

According to the Bloomberg story, U.S. officials said that publishing the documents could be a threat to national security.

"Pentagon says it expects 'nothing new' in next Wikileaks dump. 'Nothing new' to THEM goes without saying," Wikileaks tweeted on Friday.

The last major WikiLeaks release was in July, when it unloaded some 90,000 secret documents pertaining to the war in Afghanistan. In March, WikiLeaks dropped the "Collateral Death" video, infamous footage that reportedly focused on the U.S. cover-up of civilian casualties.

The U.S. Department of Defense has assembled a taskforce of more than 120 officials to deal with backlash from the anticipated info leak.

"Our concern is the threat to individuals, our people, and our equipment," Pentagon spokesman Colonel David Lapan told Bloomberg. "Iraq is still trying to form a government. There are sensitivities there. So who knows what the impacts might be."

The U.S. government is urging that news sources not report this information, but it is expected to be released via the same news outlets that helped facilitate the July leak, including the New York Times, Germany's Der Spiegel, and The U.K.'s Guardian.

Wikileaks also said to watch the Bureau of Investigative Journalism, IBC, Le Monde, Al Jazeera, Chan4, SVT, CNN, BBC and more in the next few hours. "We maximise impact," the group tweeted.