Brent crude prices fell on Friday for the fourth straight session, dragged down by fresh global economic concerns and expectations a major Canadian crude oil pipeline to the United States would restart on schedule.
Concerns about the lack of progress on a Spanish bailout dampened risk appetite, helping send equities and commodity markets lower and lending support to the dollar.
Oil prices initially turned negative in early US trade following news that TransCanada Corp expected to restart the 590,000-barrel-per-day Keystone pipeline to the US market over the weekend despite poor weather hampering efforts.
The line was shut on Wednesday after an anomaly was detected, but analysts said that with US crude oil inventories healthy, the market should be able to absorb a short-term disruption with little problem. US crude stocks are nearly 11 percent above year-ago levels, according to government data.
"Because of the ample supplies of oil (in the United States), a three-day closure is not extremely bullish - if they announce a delay that's when the market will start to get a bid in it again," said Gene McGillian, analyst at Tradition Energy in Stamford, Connecticut.
Further pressure on prices came from a report showing US home resales retreated in September from a two-year high.
Oil markets have been balancing the struggling economy and weak demand against supply problems in the North Sea, which have helped lift Brent crude's premium to US oil to $US20 a barrel.
Crude prices received an early lift on news that there was another delay in the restart of the North Sea Buzzard oilfield, which is now expected to restart on October 23 after a maintenance shutdown.
Brent December crude fell $US2.28 to settle at $US110.14 a barrel. The international benchmark traded as high as $US113.27, just below the 50-day moving average of $US113.33, before dipping as low as $US110.05.
US front-month November crude lost $US2.05 to settle at $US90.05 a barrel, after finding resistance at $US93 a barrel area and testing support under $US90 near the 100-day moving average.
Brent volumes were light, about 20 per cent below its 30-day average, while US trading activity was closer to normal levels.
Gasoline and heating oil futures also fell, off 1.6 and 1.4 per cent, respectively, finding some support relative to crude prices due to concerns about supplies.
For the week, Brent lost $US4.48, or 3.9 per cent, while US crude gave up $US1.81, or 1.9 per cent. Money managers cut net long positions by nearly 3000 contracts to just over 193,000 contracts, in the week to October 16, according to data from the US Commodity Futures Trading Commission.