A World Trade Organisation panel, responding to a US complaint, found that China was inconsistent with the global body's rules when it imposed tariffs in December 2011 over alleged US dumping and subsidies.
China, the largest foreign market for US automakers after Canada, ended the tariffs in December 2013 as the WTO case progressed. But a US official said that Washington insisted that the WTO formally rule against the measures to ensure that they stay off the books.
"Americans deserve to compete on a fair and level playing field, and we will never stop fighting to ensure that our trading partners live up to the commitments they made in our international trade agreements," Froman said.
China imposed the tariffs over what it said were unfair US practices amid a raft of trade disputes. But Froman noted that the United States had won in all three cases that had come to WTO resolution, the others concerning steel products and broiled chickens.
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China in 2011 had imposed tariffs for alleged dumping - selling in a foreign market at below home-market prices - that ranged from 2.0 to 21.5 per cent. It also slapped tariffs of up to 12.9 per cent for what it said were US subsidies.
Consumers in China, unlike those in some more developed Asian nations such as Japan and South Korea, have shown a strong appetite for cars from the United States as incomes grow.
The tariffs applied to cars from Detroit's Big Three - General Motors, Chrysler and Ford Motor - and also to automobiles from BMW, Mercedes-Benz and Honda that were manufactured in the United States.