The European Union asked the World Trade Organization (WTO) on Friday to rule on tariffs that China has imposed on the import of steel tubes - the latest in a series of trade disputes between the two economic giants, dpa reported. "The EU continues its fight against unjustified Chinese trade defence measures, which do not comply with WTO rules and often seem to be motivated by retaliation," said John Clancy, a spokesman for EU Trade Commissioner Karel De Gucht. China began investigating the import of stainless steel seamless tubes shortly after the EU imposed a provisional anti-dumping duty on its imports of certain seamless pipes and stainless steel tubes from China in 2011, the European Commission wrote. The EU had approached the WTO last month over China's anti-dumping duties imposed on the import of the tubes, which are used in power stations. China imposed duties ranging from 9.7 to 11.1 per cent on European-produced steel tubes last year, over allegations that the EU was illegally undercutting prices.