Federal Reserve Chairman Ben Bernanke's comments that the central bank is ready to cut interest rates to help stave off a recession helped crude prices pare some of their losses, as did an attack on six oil industry ships by Nigerian rebels.
But prices stayed in negative territory after a tepid unemployment claims report and weak holiday sales at many large retailers, data that compounded the market's growing fears of an economic downturn.
An Energy Information Administration report that demand for crude oil and petroleum products fell last week for the third week in a row contributed to the price declines.
'Without US demand and without stronger economic growth, crude oil can't stay in the US$90s (S$100s),' said Mr James Cordier, president of Liberty Trading Group in Tampa, Florida.
Light, sweet crude for February delivery fell US$1.96 (S$2.80) to settle at US$93.71 a barrel on the New York Mercantile Exchange, after dipping as low as US$93.30 earlier.
Mr Bernanke's comments raised chances the Fed will cut rates by a half percentage point when it meets at the end of January. Lower rates tend to weaken the dollar, giving investors reason to buy oil.
Crude futures offer a hedge against a falling dollar, and oil futures bought and sold in dollars are more attractive to foreign investors when the greenback is falling.
Many analysts believe the weakening dollar helped draw speculative investors into oil markets this fall and winter, driving oil prices above US$100 a barrel last week.
Separately, the Movement for the Emancipation of the Niger Delta (Mend), a group whose attacks have crippled oil production in Africa's top exporter, said it fired on oil ships on the Bonny River. The rebels provided no further details, but threatened further attacks that will cause an 'economic tsunami' in world oil markets.
Last week, oil prices sold off sharply after a report showed employers created far fewer jobs last month than expected. -- AP