Brent oil dropped to a four-year low amid signs the Organization of Petroleum Exporting Countries isn't prepared to tackle the global supply glut. West Texas Intermediate crude slipped in New York.

Futures fell as much as 1.8 percent in London. The oil market is oversupplied, partly because of rising U.S. output, United Arab Emirates Energy Minister Suhail Al Mazrouei said today in Abu Dhabi. OPEC members including Saudi Arabia and Iraq are resisting calls to curb output and instead cut export prices to the U.S., where production is running at the highest level in more than 30 years. The group meets Nov. 27 in Vienna.

"There's uncertainty about OPEC and whether it will or will not cut production at the Nov. 27 meeting," Kyle Cooper, director of commodities research at IAF Advisors in Houston, said by phone. "They probably wouldn't have to do that much to stabilize the market but until some action is taken there's not a lot of upside for this market."

Brent for December settlement fell $1.44, or 1.8 percent, to $80.90 a barrel on the London-based ICE Futures Europe exchange at 11:38 a.m. in New York. That's the lowest level since October 2010. The volume of all futures traded was 14 percent above the 100-day average for the time of day.

WTI for December delivery dropped 73 cents, or 0.9 percent, to $76.67 a barrel on the New York Mercantile Exchange. Volume was 8.6 lower than the 100-day average. The U.S. benchmark traded at a $4.17 discount to Brent, compared with $4.94 at yesterday's close.