The United States on Wednesday challenged a Chinese export subsidy program for products including textiles, medical products and agriculture, alleging the support was illegal under international trade law.

U.S. Trade Representative Michael Froman said starting a dispute process at the World Trade Organization would help ensure a level playing field. There are already 24 disputes before the WTO involving the United States and China, 15 of them brought by the United States.

"This policy appears to break the rules that China committed to uphold when they joined the WTO, and it's a policy that injures American workers, farmers, ranchers, and businesses - really anyone who plays by the rules and wants to compete fairly, on the merits of their hard work and the quality of their products," Froman said in a statement.

USTR said China's "Demonstration Bases-Common Service Platform" program appeared to give forbidden export subsidies to industries including textiles, apparel and footwear; advanced materials and metals; light industry; specialty chemicals; medical products; hardware and building materials; and agriculture.

The program gave out free and discounted services, cash grants and other incentives, USTR said. It added that some companies had received at least $635,000 worth of benefits annually and China had given almost $1 billion over a three-year period to suppliers that agreed to provide discounted or free services to Chinese companies, including exporters participating in the program.