According to Reuters, OPEC cut its forecast for world demand for its crude oil next year due to the slowing global economy, building a case for further oil supply cuts to prop up prices. In a monthly report, OPEC said it expected 2009 demand for its oil to average 30.92 million barrels a day. That is 220,000 bpd less than last month''s forecast and 920,000 bpd less than its estimate for 2008 demand. The revision comes in response to mounting evidence that the world economy is far weaker than previously thought, undermining oil demand and prices. Oil has slid to around $57 a barrel from a record high of $147.27 in July. In the report, the Organization of the Petroleum Exporting Countries, source of two in every five barrels of oil, also cut its forecasts for growth in world oil demand this year and next. The report lowered OPEC''s 2009 forecast for global oil demand growth by 270,000 bpd to 490,000 bpd and trimmed the 2008 estimate by 260,000 bpd to 290,000 bpd. With the latest downward revision, OPEC has almost halved its forecast for 2009 oil demand growth from its first prediction of 900,000 bpd given in June. Oil prices fell after the report was released, but later pared losses on news that pirates took control of a large Saudi-owned oil tanker in the