Washington is accusing Beijing of unfairly tinkering with the prices of corn, wheat, and rice in ways that hurt U.S. exports and farmers. President Barack Obama says "unfair" Beijing's subsidies distort prices, lead to over production by Chinese farmers and "disadvantage" American farmers who export the same crops around the world. Tuesday U.S. Trade Representative Michael Froman and Agriculture Secretary Tom Vilsack said China's use of "market price support" is $100 billion higher than commitments China made when it joined the WTO. “We will aggressively pursue this challenge on behalf of American farmers and hold the Chinese government accountable to the standards of fair global trade,” Froman said. Higher Chinese production reduces the market in China for U.S.-grown products. China has grown to a $20 billion market for U.S. agricultural products, but U.S. officials say it could and should be much larger. America's rice, wheat, and corn industries support 200,000 U.S. jobs. This is the 14th complaint brought by the U.S.T.R. against China since 2009. Washington says it has won all the disputes decided so far, and has filed more trade cases than any other WTO nation. Obama said the U.S. is confident the case "should bring an end to China's illegal subsides, remove significant barriers on American exports and level the playing field for American farmers and their families who rely on the rice, wheat and corn industries and the hundreds of thousands of jobs they help support."