Using an average of $50 a barrel, the report says the discrepancy was valued at $5 million to $15 million daily, the paper said.
The draft report comes as the U.S. and Iraqi governments are under pressure to show progress in Iraq by raising oil production levels, which have been well below the U.S. goal of 3 million barrels a day. Virtually the entire economy of oil-rich Iraq is dependent on oil revenues.
The New York Times said the draft U.S. government report it obtained was prepared by the United States Government Accountability Office with the help of government energy analysts. The paper says the report is expected to be released within the next week.
It does not conclude what happened to the missing fraction of the roughly 2 million barrels pumped by Iraq each day, but its findings are expected to reinforce long-standing suspicions that smugglers, insurgents and corrupt officials control significant parts of the country's oil industry, the paper said.
It said the draft report also covered alternative explanations for the billions of dollars worth of discrepancies, including the possibility that Iraq has been overstating its oil production.