The Pentagon has asked the US Justice Department to join an inquiry into alleged fuel overcharging by Halliburton according to a report in the Wall Street Journaltoday.
Citing a senior justice official, the Journalsaid the department was "expected" to take up the case, but that it was unclear which division would look at it because allegations involved both civil and criminal violations.
Halliburton, the Texas oil services company once run by US vice president, Mr Dick Cheney, is under investigation by the US military's inspector general for overcharging for fuel taken into Iraq.
Halliburton unit Kellogg Brown and Root has more than $6 billion worth of work in Iraq, including a major logistical contract to support US troops which involves tasks from serving meals to doing laundry.
A report by auditors of the US military said the company submitted a $2.7 billion proposal that did not contain "current, accurate and complete data regarding subcontract costs."
Earlier this year the company said it would hold back on billing for tens of millions of dollars in meals while it established with auditors whether it had charged too much.