Crude prices slipped today to multi-year lows owing to a build-up in supplies while the dollar rallied in response to a strong US jobs report. US benchmark West Texas Intermediate for November delivery was down five cents at 89.69 dollar. On Friday it closed below 90 dollar for the first time since April 2013. Brent North Sea crude eased 36 cents to 91.95 dollar, a two-year low.While output surges in the United States owing to oil shale extraction, exports are on the rise in Russia, Libya and Kurdistan. Also, Saudi Arabia cut prices for the fourth straight month last week to defend its market share,suggesting it is unlikely to cut production any time soon. Both Brent and New York contracts have shed about 15 percent in the past three months.