Oil prices fell more than 4% on Monday as deepening economic worries countered expectations that OPEC would agree to its biggest supply cut ever when the group meets in Algeria this week.
US crude fell $US1.77 to $US44.51 a barrel.
London Brent crude fell $US1.81 to trade at $US44.60 a barrel.
Dealers said they were eyeing stock market losses amid worries about the world economy, even as OPEC and top non-OPEC producer Russia said they likely would agree to slash output.
The financial turmoil has cut growth in energy demand and contributed to a slide in oil prices of more than $US100 per barrel since the peak over $US147 in July.