Brent crude extended losses below $80 a barrel, dropping to a four-year low amid signs that OPEC remains unwilling to reduce output to ease a supply glut. West Texas Intermediate fell in New York.

Futures slid as much as 1.3 percent in London to the lowest since September 2010. Saudi Arabia is committed to a stable market and speculation of a price war within the Organization of Petroleum Exporting Countries “has no basis in reality,” Oil Minister Ali Al-Naimi said Wednesday in Acapulco, Mexico. Crude stockpiles in the U.S., the world's biggest oil consumer, probably rose for a sixth week, a Bloomberg News survey shows before government data Thursday.

Oil has collapsed into a bear market as leading OPEC members resisted calls to cut production and instead reduced export prices to the U.S., where output has climbed to the highest level in more than three decades. Venezuela, Libya and Ecuador have asked for action to prevent crude from falling further. The group is scheduled to meet this month in Vienna.