The Pentagon has assembled a 120-member team to prepare for the expected publication of some 400,000 Iraq war documents on the Wikileaks website.
The documents are thought to concern battle activity, Iraqi security forces and civilian casualties.
Colonel Dave Lapan, a Pentagon spokesman, said the timing of the leak remained unclear but are preparing for it to be as early as Monday or Tuesday - a possibility raised in previous WikiLeaks statements.
The Pentagon said on Sunday it wants the documents back to avoid "potentially damaging" information being released.
Lapan said the files were from an Iraq-based database that contained "significant acts, unit-level reporting, tactical reports, things of that nature".
If confirmed, the leak would be much larger than the record-breaking release of more than 70,000 Afghan war documents in July, which stoked debate about the nine-year-old conflict but did not contain major revelations.
Spencer Ackerman, a journalist who has covered Wikileaks extensively, told Al Jazeera this particular release of documents would dwarf Wikileaks' July publication of more than 70,000 Afghan war files.