The price of Brent crude oil dropped $2 to a four-year low, under $76 a barrel, as OPEC output cut uncertainties continue to grow despite worldwide market oversupply.
Reuters reported that benchmark Brent futures were down by $1.60 at $76.15 a barrel, while US crude fell $1 to $71.89.
Sources close to OPEC said its ministers were unlikely to agree to a production cut at their policy meeting in Vienna later today.
Iraq Oil Minister Abel Abdel Mehdi said he saw oil prices to be between $65 and $70 a barrel.
Several commodity fund managers believe that oil prices may slide to $60 per barrel if OPEC does not agree to an output cut.
Reuters analyst Wang Tao said he expected US oil to drop to $63.85 per barrel in the next four weeks.
Analysts said increasing US shale oil production, as well as rising Chinese and US oil stocks, have boosted available supplies affecting the value of crude oil.
Consultancy Energy Aspects said US crude output averaged 8.86 million barrels per day in September.
The US Energy Information Administration said crude inventories in the US increased by 1.9 million barrels in the week to 21 November.