The unpopular way the United States deals with unfairly priced imports suffered a new blow at the World Trade Organisation (WTO) on Friday when Japan said it wanted to levy extra duties in retaliation.

Japan said it was asking the trade body for permission to slap on up to $250 million a year in extra duties or tariffs on U.S. goods to retaliate for the way Washington sets duties on imports it says are being dumped in the U.S. market.

The U.S. methodology, known as "zeroing", which calculates anti-dumping duties, is opposed by all other 151 WTO member states and has been legally challenged a number of times.

Tokyo's request will be discussed at a meeting of the WTO's Dispute Settlement Body on Jan. 21.

"We filed the request for authorisation to retaliate," Koji Saito, a diplomat in Japan's WTO mission, told Reuters. "As we see it, the U.S. has failed to comply with the WTO's ruling."

Zeroing refers to the practice of looking only at imports priced at a lower level than in their home markets and ignoring, or "zeroing", similar products that actually cost more at home, when making comparison to establish the level of dumping.

Critics say this results in unfairly high anti-dumping margins.

Zeroing has prompted a furious row in the WTO's Doha round negotiations to open up world trade, and seen a WTO dispute panel ignore rulings by its top court, the Appellate Body.

The Appellate Body has repeatedly ruled against zeroing, but Washington disagrees with its jurisprudence and wants the WTO to make clear the method is permissible in the new trade rules being negotiated in the Doha round.

ZERO CHANCE?

Trade experts say this will not be easy, given the dozen cases the United States has lost over the issue, and the near-universal opposition to it among other WTO members.

"The hard fact for the United States is they've hit zeroing in the Appellate Body repeatedly," said trade dispute expert Brendan McGivern, a partner at law firm White & Case.

"To get back through negotiation what you've lost in litigation is very difficult."

Japan's request is the latest move in a dispute brought by Tokyo against the United States in 2004. The Appellate Body ruled in January 2007 against the United States in the case.

Following that ruling Washington was obliged to bring its trade measures in line with WTO rules by Dec. 24 last year.

Zeroing is a way of calculating compensatory duties on imports that are "dumped" or sold more cheaply than in their home market. The investigating authorities often look at a range of transactions to establish the anti-dumping margin.

The original dispute centres on U.S. anti-dumping measures against Japan's bearings industry, but Saito said Japan reserved the right to retaliate against the full range of U.S. goods.

In another dispute, New Zealand is seeking a ruling from the WTO on whether tough Australian sanitary rules on apple imports break global trading rules.

In the first WTO dispute between Australia and New Zealand, Wellington is asking the Jan. 21 meeting of the Dispute Settlement Body to set up a panel to rule on the row.