Oil prices slipped in New York and London on Thursday, erasing the previous session’s gains that had followed a U.S. government inventory report. September-delivery West Texas Intermediate closed at $63.88 a barrel on the New York Mercantile Exchange, down 47 cents, or 0.73%. October Brent settled at $66.43 on ICE Futures Europe, 46 cents lower, or 0.69%. Refined products also ended lower. September gasoline futures finished at $2.0775 a gallon, while September diesel settled at $2.2668. Natural-gas contracts for the same month closed at $3.067 per million British thermal units. On Wednesday futures had advanced as much as 2% after Energy Information Administration data showed declines in U.S. gasoline and diesel inventories, but the rally faded amid concern about global demand and robust supplies.