The report says that nearly 26,000 Iraqis have been killed or wounded in attacks by insurgents, with an estimated 26 casualties a day between January and March of last year, rising to 64 a day in the run up to the referendum on the new constitution.
This contradicts the Pentagon's assertion that the security situation in Iraq is improving - and that appearances to the contrary reflect the media's focus on bombings in and around Baghdad.
Previously, the US military has insisted it kept records of the casualties among only its own personnel, and avoided discussion about civilian tolls. It also refuses to release information on the number of Iraqi civilians killed or wounded by US forces.
Washington and London have regularly doubted independent estimates of the number of Iraqis killed since the 2003 invasion.
Pentagon officials said the report was only a rough estimate and did not distinguish between civilian casualties and members of Iraq's nascent security services killed or wounded in insurgency attacks.
"They have begun to realise that when you focus only on the US it gives the impression that the US doesn't care about Iraqis," Anthony H. Cordesman, a military expert at the Centre for Strategic and International Studies, a research group in Washington told The New York Times.
Greg Hicks, a Pentagon spokesman, trying to play down the significance of the information, said: "It's a kind of a snapshot. The Defence Department doesn't maintain a comprehensive or authoritative count of Iraqi casualties." The estimates in the graph were based on casualty reports filed by US and allied forces who responded to attacks, but Mr Hicks noted that troops did not respond to all attacks.
The graph appeared in a quarterly audit of Iraq operations. Analysis carried out by the independent group Iraq Body Count, which compiles statistics for civilian casualties based on reports by news outlets, suggests the figure of 26,000 casualties would correspond to a death toll of nearly 6,500 - based on a ratio of one death for every three casualties.
This figure is lower than Iraq Body Count's estimate for the same period of 11,613, which includes those killed by US and allied forces. It is also lower than the Iraqi Interior Ministry estimate for the period from August 2004 to May this year of 8,175.
The appearance of the graph will increase pressure on the Pentagon to be more open in releasing data on fatalities in Iraq.
Hamit Dardagan from Iraq Body Count told The New York Times: "We now know that the US military does keep records of Iraqi civilian deaths. There seems to be no obvious reason for keeping them a secret."
* Ghalib Abdul Mehdi, a brother of Adel Abdul Mehdi, a prominent Shia politician, and his driver were killed yesterday in Baghdad in an attack claimed by al-Qa'ida in Iraq. In a separate incident, Qais Dawoud Hassan, the deputy Trade Minister was wounded in an ambush.The attacks came one day after a bomber killed 30 people after luring them to a truck bomb disguised as a date vendor's van in Howaider, north of Baghdad.