The European Commission, which looks after trade matters for the 15-nation EU, sought an investigation on Tuesday at the Geneva-based World Trade Organisation into how US antidumping duties are calculated. 

"Several hundred million dollars of trade is involved," the Commission said in a statement accompanying the request for a trade panel to decide on the rights and wrongs of the case. 

But the investigation, which can take at least six months, will not be launched immediately because the United States exercised its right under WTO rules for a brief delay. 

However, it will be automatically triggered after the next meeting of the WTO's disputes settlement body on 19 March . 

'Zeroing'

The EU is attacking a practice known as zeroing, which raises the amounts of duties countries have to pay if they are found by Washington to have dumped goods on the US market. 

The Commission said products such as steel, ball bearings, chemicals and pasta were being hit by the zeroing method. 

The dispute adds to several high profile transatlantic trade fights, one of which comes to a head on 1 March . 

That case involves a threat of $200 million of EU sanctions on US goods unless Congress changes legislation which gives tax breaks to exporters, but which was ruled illegal by the WTO.