An extra $1bn (£603m) will be needed if Iraq's oil output is to be restored to pre-war levels by the end of next year, a senior Coalition Provisional Authority official has been reported as saying.
The sum would be in addition to the $1.5bn already allocated for work this year and next to ensure current oil production and export levels are maintained.
Iraqi oil has taken longer than expected to return to world markets, partly because of sabotage against pipelines and other facilities.
US authorities have blamed the attacks on elements loyal to former president Saddam Hussein who are attempting to disrupt the US-led administration of the country.
Iraqi crude oil exports are running at one million-1.2 million barrels a day (b/d), the official was reported by Reuters news agency as saying.
Pre-war capacity was three million b/d, of which 2.5 million b/d was exported.