China won a World Trade Organization ruling on Friday after the United States decided not to contest the facts of its complaint against US anti-dumping duties on shipments of diamond saw blades and frozen warm-water shrimp from China.

China's complaint, which it made in February 2011, was based on the fact that the US anti-dumping duties were calculated in a way that has repeatedly been ruled as illegal under WTO rules.

The WTO dispute panel that examined the case said the US Department of Commerce had acted inconsistently with WTO rules and said it should bring its rules into line.

The United States has said that its calculation method, known as "zeroing", is superior to the WTO's approved methodology, but it has nevertheless promised not to use it in future, after losing numerous legal rulings over the issue.

A country is usually considered to be dumping a certain product if the export price is unfairly low, which generally means below the price in the country where it came from.

The WTO's approved method uses an average price for the export product in question, while the US method considers only those products that are cheaply priced, disregarding (or "zeroing") all prices that are above the home market.

That means it only takes into account the low-priced goods and effectively inflates the apparent amount of dumping, or even finds dumping where there is none.

The United States is still involved in several other WTO cases involving zeroing, including a South Korean complaint about corrosion-resistant carbon steel flat products which is currently being examined by a WTO dispute panel.