WikiLeaks is preparing to release 400,000 intelligence files on the Iraq war and the Pentagon is bracing for its biggest ever security breach of classified documents, it was reported here. The latest WikiLeaks disclosure will eclipse the recent release of over 70,000 classified US military files on the Afghanistan war, Daily Telegraph reported Monday from Washington. US has established a task force of 120 people to assess the potential implications and damage of the disclosure of the documents. Pentagon spokesman, Col. Dave Lapan, said the timing of the leak remained unclear but the Defence Department was ready for it as early as Monday or Tuesday. The latest files may be on tactical reports database in Iraq that lists SIGACTS (Significant activities) relating to major military operations, movement of personnel and alliances with key tribal figures and allies, the media report said. WikiLeaks expose on Afghanistan in July had led Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, to warn that the website may cause the deaths of American troops and Afghan civilians named as cooperating with the coalition forces as the documents contained names. The documents showed NATO concerns that the Pakistan intelligence services has backed the Taliban fight against US forces in Afghanistan. Robert Gates, the US defence secretary, has said that the leak of classified information from Jan 2004 to Dec 2009 hadn't revealed any sensitive intelligence sources or methods. Following the WikiLeaks expose, an investigation was launched. Private Bradley Manning, who worked as a US Army intelligence analyst in Iraq, was arrested and charged with leaking a classified video of a 2007 helicopter attack that killed a dozen people in Iraq.