Oil prices fell in Asia today after the Organisation of Petroleum Exporting Countries warned of an oversupply as uncertainty surrounds the outlook for the global economy. New York's main contract, light sweet crude for delivery in January fell 19 cents to 86.58 dollars a barrel and Brent North Sea crude for January delivery shed 15 cents to 109.35 dollars. OPEC — which produces more than a third of the world's oil — late yesterday announced at a meeting in Vienna that it was holding its oil output ceiling at 30 million barrels per day due to demand uncertainties