BERLIN (Reuters) – You cannot find any basis in World Trade Organisation rules for U.S. tariffs on steel and aluminium, nonetheless the European Union should proceed cautiously when resolving the measures, WTO deputy director-general, Karl Brauner, told a German magazine.

" no basis in WTO law for that tariffs imposed via the U.S.," Brauner told Wirtschaftswoche.

"A trade war is not really automatic. A couple of seconds happens an action is reacted to – and perchance triggers a series reaction," he said, adding the fact that EU should "be extremely cautious and fine-tune (its) planned tariffs to lower the collateral problems for local businesses."