Oil fell by the most since 1991 on Monday after Saudi Arabia started a price war with Russia by slashing its selling prices and pledging to unleash its pent-up supply onto a market reeling from falling demand because of the coronavirus outbreak. Brent crude futures fell by as much as $14.25, or 31.5%, to $31.02 a barrel. That was the biggest percentage drop since Jan. 17, 1991, at the start of the first Gulf War and the lowest since Feb. 12, 2016. U.S. West Texas Intermediate (WTI) crude fell by as much as $11.28, or 27.4%, to $30 a barrel. That was also the biggest percentage drop since the first Gulf War in January 1991 and the lowest since Feb. 22, 2016. It was trading at $32.61. Saudi Arabia, the world's biggest oil exporter, is attempting to punish Russia, the world's second-largest producer, for balking on Friday at production cuts proposed by the Organization of the Petroleum Exporting Countries (OPEC). OPEC and other producers supported the cuts to stabilize falling prices caused by the economic fallout from the coronavirus outbreak. Saudi Arabia, Russia, and other major producers last battled for market share like this between 2014 and 2016 to try to squeeze out production from the United States, now the world's biggest oil producer as flows from shale oil fields doubled the country's output during the last decade. Saudi Arabia has opened the war by cutting its official selling prices for April for all crude grades to all destinations by between $6 to $8 a barrel. The spread to other major economies such as Italy and South Korea and the burgeoning cases in the United States has increased the concerns that oil demand will slump this year.