NEW YORK, Dec. 8 (Xinhua) -- Oil prices extended gains on Friday, as strong demand and geopolitical uncertainties have provided support to the market. The West Texas Intermediate for January delivery increased 67 U.S. cents to settle at 57.36 dollars a barrel on the New York Mercantile Exchange, while Brent crude for February delivery rose 1.20 dollars to close at 63.40 dollars a barrel on the London ICE Futures Exchange.