* Case involves imports from non-market economy
* China complained of double penalty
(Adds detail, background)
GENEVA, Dec 3 (Reuters) - China has appealed against a ruling by a World Trade Organization panel upholding the right of the United States to impose extra duties on Chinese goods that Washington said were unfairly priced and subsidised, an official at China's WTO mission said on Friday.
The appeal, launched on Dec. 1 in the complex case involving treatment of goods from a country that is not a market economy and where the state influences prices, demonstrates China's increasing assertiveness in the global trading system.
China had challenged the way the United States calculated the duties and the fact that it suffered a double penalty of anti-dumping duties for unfairly priced goods and countervailing duties for subsidised products.
But the original ruling published on Oct. 22 had backed the right of an importer to set duties on goods from non-market economies to compensate for unfair pricing and for subsidies -- something a U.S. court had previously struck down.
The two-year-old dispute involved duties imposed by the United States on imports of Chinese steel pipes, off-road tyres and woven sacks.
Under normal practice, the WTO's appellate body will issue a ruling on the appeal within 90 days.
As the world's largest exporter, China is frequently the target of trade actions by other countries, but it has been building up expertise in handling the global trading system by launching its own cases and appealing adverse judgments. (Reporting by Jonathan Lynn; editing by Stephanie Nebehay and Tim Pearce)