The US Department of Commerce said the duties effectively would increase by more than five-fold the import prices on Chinese-made cold-rolled flat steel products, which totaled US$272.3 million last year.
Cold-rolled steel is primarily used in automotive body panels, appliances, shipping containers and construction.
The rulings come amid escalating US-China trade tensions, especially in the steel sector, where both US and European producers claim China has distorted world pricing by dumping its excess output abroad as demand at home slows.
The complaint was filed in July last year by major US producers United States Steel, AK Steel Corp, ArcelorMittal USA, Nucor Corp and Steel Dynamics Inc.
Chinese companies affected by the duties include Baosteel Group (寶鋼集團), Angang Group Hong Kong Holdings Ltd (鞍鋼集團香港控股) and Benxi Iron and Steel (Group) Special Steel Co Ltd (本溪鋼鐵集團特殊鋼). Among Japanese producers affected are Nippon Steel & Sumitomo Metal Corp and JFE Steel Corp.
For Chinese cold-rolled steel imports, the department upheld its preliminary anti-dumping duties of 265.79 percent, but increased its preliminary anti-subsidy duties to 256.44 percent from 227.29 percent.
In a separate case, US Steel is seeking to halt all imports from China's top steelmakers.
In a complaint to the US International Trade Commission, the US steelmaker called on regulators to investigate dozens of Chinese producers and their distributors for allegedly conspiring to fix prices, stealing trade secrets and circumventing trade duties by false labeling.
Beijing has defended itself against the allegations, saying it has done enough to reduce steel capacity and blaming global excess and weak demand for the industry's woes.
