Investing.com - West Texas Intermediate oil futures plunged below the key $80-a-barrel level on Monday, after Goldman Sachs slashed its 2015 price forecast, citing rising global supplies.
On the New York Mercantile Exchange, crude oil for delivery in December traded at $79.77 a barrel during U.S. morning hours, down $1.24, or 1.53%.
WTI prices fell to a session low of $79.46 a barrel earlier, the weakest level since October 16, when futures hit a two-year low of $79.10.
Elsewhere, on the ICE Futures Exchange in London, Brent for December delivery tumbled $1.26, or 1.47%, to hit $84.87 a barrel.
Wall Street investment bank Goldman Sachs cut its oil price forecast for WTI in the first quarter of next year by $15 to $75 a barrel.
The investment bank expects Brent prices to average $85 a barrel in the first three months of 2015, down from a previous estimate of $100.
Goldman analysts expect WTI to fall as low as $70 a barrel and Brent to $80 in the second quarter of 2015, when it expects oversupply to be most pronounced.
London-traded Brent prices have fallen nearly 27% since June, when it climbed near $116, while WTI futures are down almost 26% from a recent peak of $107.50 in June.
Concerns over weakening global demand combined with indications that the Organization of the Petroleum Exporting Countries will not cut output to support oil markets have weighed on prices in recent weeks.
OPEC oil output hit a two-year high of 31 million barrels per day in September, led by higher production from Iraq and Libya.
Some market analysts believe that only a cut in production by the oil cartel will halt the decline in prices.
Oil ministers from the 12-member group are scheduled to meet in Vienna on November 27 to consider whether to adjust their production target for early 2015.