United States Steel Corporation has filed a complaint with US regulators against the biggest Chinese steel producers, accusing them of conspiring to fix prices, stealing trade secrets and skirting duties on imports in the US with false labelling. The big steelmaker is alleging illegal unfair competition by the Chinese producers and their distributors, and is seeking “the exclusion of all unfairly traded Chinese steel products from the US market.”

US Steel has lodged the complaint with the US International Trade Commission. Normally the independent federal agency decides within 30 days whether or not to act. The case would go before an administrative law judge at the agency if it decides to proceed.

Pittsburgh-based US Steel brought the complaint under a section of the Depression-era Tariff Act, which empowers the US Government to bar imports deemed to be anti-competitive. The provision has mostly been used against perceived violations of intellectual property rights. “We have said that we will use every tool available to fight for fair trade,” US Steel president and CEO Mario longhi said in a statement.

The United Steelworkers union voiced support for the company’s action. “America’s steel sector is under attack by China,” union president leo Gerard said in a statement. “Repeated illegal and predatory trade practices have devastated production and employment in steel and many other sectors.”

US Steel and the union, though sometimes at odds on labor issues, have been united in decrying low-priced steel imports from China and elsewhere. The sharp decline in oil prices in recent months has crimped oil and gas drilling, reducing the demand for steel. US Steel has taken cost-cutting measures including closing and idling mills across the country, and laying off thousands of workers.