GENEVA/WASHINGTON (Reuters) - China won the bulk of a World Trade Organization complaint against certain U.S. methods of determining anti-dumping duties on Chinese products in a WTO dispute panel ruling released on Wednesday.

Cargo containers at the Port of Los Angeles in a file photo. REUTERS/Bob Riha, Jr.

China brought the complaint in December 2013, one of a string of disputes challenging Washington’s way of assessing “dumping,” or exporting at unfairly cheap prices.

Specifically, the panel found fault with the U.S. practices of determining dumping margins in certain cases of “targeted dumping,” in which foreign firms cut prices on goods aimed at specific U.S. regions, customer groups or time periods.

Dumping is normally found when a foreign producer’s U.S. prices are lower than its home market prices for the same or similar goods, or when the imports are sold at prices below production costs.

The panel ruled against the U.S. Commerce Department’s practise of “zeroing” in cases involving targeted dumping. In zeroing, the department typically assigns a value of zero any time a producer’s export price is above that producer’s normal home market price, partly to account for freight and customs charges.

In practice, the zeroing methodology tends to increase the level of U.S. anti-dumping duties on foreign producers.

Some points of China’s argument were rejected by the WTO panel, including a claim that the Commerce Department systematically punishes Chinese state enterprise by assigning them high anti-dumping rates.

Either side can appeal the ruling within 60 days.

China’s Ministry of Commerce welcomed the ruling saying that the WTO panel had “upheld China’s principal claims” on the unlawfulness of targeted dumping and the separate rate applied in certain U.S. anti-dumping measures.

The dispute related to several industries including machinery and electronics, light industry, metals and minerals, with an annual export value of up to $8.4 billion, it said.

“The United States is disappointed by these findings,” a spokesman for the U.S. Trade Representative’s office said in a statement.

“We will carefully review the report and consider next steps. Nothing in the report will undermine the commitment of the United States to impose antidumping duties to address injurious dumping,” the USTR spokesman added.