WASHINGTON — The United States is challenging China at the World Trade Organization, alleging that the Chinese government unfairly subsidizes exports in seven industries.

The Office of the U.S. Trade Representative said China designates certain export companies as “demonstration bases” that receive free or discounted services from suppliers. The U.S. says China paid the suppliers almost $1 billion over three years to provide those services.

Getting help are textile and clothing makers, advanced materials and metals companies, light industrial firms, specialty chemical manufacturers, medical product makers and agricultural firms.

The U.S. says the subsidies violate WTO rules.