Crude futures slipped Monday, as oil cartel OPEC announced it would further increase output by half a million barrels daily from next month to help meet an anticipated demand surge in the second half of the year. Light, sweet crude for the May contract on the New York Mercantile Exchange fell 17 cents to US$53.15 a barrel, late afternoon in Asia. Heating oil prices fell marginally to US$1.4914 a gallon (3.8 liters), the Associated Press reported. "Kuwait believes that the increase in production is still possible and may come in May due to the expected rise in demand by about 1 million barrels per day in the third quarter," OPEC President Sheikh Ahmad al-Fahd al-Sabah, also Kuwait's oil minister, said Sunday. Qatari Oil Minister Abdullah al-Attiyah also said at the weekend that a second output increase ahead of the cartel's June 15 meeting was still possible. Recently, the 11-member cartel has been attempting to counter frequent price surges and a jittery market with announcements of production increases. Demand is expected to rise in the third quarter due to the onset of the summer driving season in the United States, the world's biggest crude oil consumer. Last week, the U.S. Energy Department said the nation's inventory of crude oil grew by 2.4 million barrels to 317.1 million barrels, or 8 percent higher than last year. OPEC raised output limits by 500,000 barrels per day in March to 27.5 million barrels per day in a bid to cool prices. It left room for a second 500,000 barrels per day increase before a June meeting if prices failed to drop below US$55. The group began talks on the second rise last weekend and said then it could decide within two weeks.