World oil prices weakened on the back of poor economic data, ahead of the latest energy inventories report and an interest rate decision in top consumer the US. The market remained subdued, despite a forecast from the International Energy Agency (IEA) that economic recovery, mainly in Asia, would push up global oil demand by 1.4% a year until 2015. New York's main futures contract, light sweet crude for delivery in August, fell eight cents to $77.77 a barrel. The July contract had expired yesterday.Brent North Sea crude for August delivery was down four cents at $78 in midday deals. The US government's Department of Energy (DoE) will publish its report on American oil inventories for the week ending June 18 later today. The weekly snapshot is a key market indicator of demand because the United States consumes far more oil than any other country.