The bold prediction, while made previously by some analysts, is significant because the IEA advises 28 countries on energy policy and its oil demand forecasts are closely watched by traders and policymakers.

"When we look at the OECD countries -- the U.S., Europe and Japan -- I think the level of demand that we have seen in 2006 and 2007, we will never see again," Fatih Birol told Reuters in a telephone interview.

"There may be some zig zags up and down but as a trend I think it will be a downward trend in terms of oil consumption."

Flat or declining OECD demand may ease any strain on oil prices caused by ever-growing consumption in emerging economies. The Organization for Economic Cooperation and Development (OECD) countries will account for 53 percent of world demand in 2010, according to the IEA.