LONDON --- Concerns about a possible U.S. recession have made the task of forecasting OPEC oil demand this year more complicated, the group said today. As a result, OPEC is less likely to decide next month to boost supplies, Reuters reported. In its monthly market report, OPEC predicted that world economies will grow by 4.7 percent this year --- down from 5.3 percent in 2007. "With mounting evidence of a slowdown in U.S. economic expansion at year-end, fears of a downright recession have multiplied," the report said. Oil prices have dropped about 12 percent from a record high of $100.09 a barrel earlier this month. Fears about a U.S. economic slowdown have convinced investors that fuel demand will likely decrease in the coming months. At roughly $87 a barrel, oil prices have removed pressures on OPEC to decide to increase supplies when the group meets in Vienna Feb. 1, Reuters reported.