NEW YORK, Jan. 29 (Xinhua) -- Oil prices slid Monday as a rising U.S. oil output weighed on the market.

The number of rigs operating in U.S. oil fields added by 12 to a total of 759 rigs last week, marking the highest level since August, oilfield service firm Baker Hughes said in its weekly report on Friday.

Meanwhile, U.S. crude output rose by 128,000 barrels a day to 9.878 million barrels a day in the week which ended Jan. 19, according to the U.S. Energy Information Administration (EIA).

Many analysts expected that the U.S. crude output would surpass 10 million barrels a day soon, which weighed on investor sentiment.

The West Texas Intermediate for March delivery decreased 58 U.S. cents to settle at 65.56 dollars a barrel on the New York Mercantile Exchange, while Brent crude for March delivery lost 1.06 dollar to close at 69.46 dollars a barrel on the London ICE Futures Exchange.