Crude prices edged down on Monday as rising U.S. drilling activity could led to a further increase in U.S. output, countering OPEC-led production cuts.
February Brent crude futures slid 10 cents to $63.30 per barrel by 1115 GMT.
January West Texas Intermediate (WTI) crude futures lost 26 cents to $57.10 per barrel.
Goldman Sachs analysts predict that production of oil outside OPEC will increase by 550,000 barrels per day in the fourth quarter, primarily due to the launch of new projects in Canada and Brazil. In addition, production in the U.S. will increase by 280 000 barrels a day.