NEW YORK, Dec. 18 (Xinhua) -- Oil prices settled mixed Monday as traders eyed an oil-worker strike in Nigeria.

The West Texas Intermediate for January delivery decreased 0.14 U.S. dollar to settle at 57.16 dollars a barrel on the New York Mercantile Exchange, while Brent crude for February delivery added 0.18 dollar to close at 63.41 dollars a barrel on the London ICE Futures Exchange.