* U.S. oil heads for worst fall on record
* Prices down by as much as 34%
* Saudi Arabia slashes prices for its oil exports
* Graphic on major oil price milestones: https://tmsnrt.rs/39Aq3GJ (Adds charts, graphic, comment, updates prices)
TOKYO, March 9 (Reuters) - Oil prices plummeted around 30% on Monday, with U.S. oil heading for its biggest loss on record, after Saudi Arabia slashed prices and set plans for a dramatic increase in crude production in April.
Prices fell by as much as a third following Saudi Arabia's move to start a price war after Russia balked at making the further steep output cuts proposed by OPEC to stabilize oil markets hit by worries over the global spread of the coronavirus.
Brent crude futures were down $13.29, or 29%, at $31.98 a barrel by 0433 GMT, after earlier dropping to $31.02, their lowest since Feb. 12, 2016. Brent futures are on track for their biggest daily decline since Jan. 17, 1991, at the start of the first Gulf War.
U.S. West Texas Intermediate (WTI) crude fell by $13.29, or 32%, to $27.99 a barrel, after touching $27.34, its lowest since Feb. 22, 2016. The U.S. benchmark is potentially heading for its biggest decline on record, surpassing a 33% fall in January 1991.
"I think all forecasts are out the window," said Jonathan Barratt, chief investment officer at Probis Securities in Sydney. "It seems like a race to the bottom to secure order(s)."
The disintegration of the grouping called OPEC+ - made up of OPEC plus other producers including Russia - ends more than three years of cooperation on supporting the market, most recently to stabilize prices under threat from the economic impact of the coronavirus outbreak.
Saudi Arabia plans to boost its crude output above 10 million barrels per day (bpd) in April after the current deal to curb production expires at the end of March, two sources told Reuters on Sunday.
The world's biggest oil exporter is attempting to punish Russia, the world's second-largest producer, for not supporting the production cuts proposed last week by the Organization of the Petroleum Exporting Countries (OPEC).
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, which has grown to become the world's biggest oil producer as flows from shale oil fields doubled its output over the last decade.
"This clearly is the start of a price war, and the Saudis were quick to react over the weekend, reducing their April official selling price for crude oil significantly," ING Economics said in a note.
Saudi Arabia over the weekend cut its official selling prices for April for all crude grades to all destinations by between $6 and $8 a barrel.
VIRUS IMPACTS DEMAND
Meanwhile, China's efforts to curtail the coronavirus outbreak has disrupted the world's second-largest economy and curtailed shipments to the biggest oil importer.
And the spread of the virus to other major economies such as Italy and South Korea and the growing number of cases in the United States have increased concerns that oil demand will slump this year.
Major banks such as Morgan Stanley and Goldman Sachs have cut their demand growth forecasts, with Morgan Stanley predicting China will have zero demand growth in 2020. Goldman sees a contraction of 150,000 bpd in global demand.
Goldman Sachs cut its forecast for Brent to $30 for the second and third quarters of 2020.
In other markets, the dollar was down sharply against the yen, Asian stock markets were set for big falls, and gold rose to its highest since 2013 as investors fled to safe havens.
(Reporting by Aaron Sheldrick; Additional reporting by Scott DiSavino and Shu Zhang; Editing by Diane Craft, Christian Schmollinger and Tom Hogue)