The United States said Monday it had appealed a World Trade Organization ruling that favoured Canada in a longstanding battle over lumber imports, describing the decision as "deeply flawed".  The WTO's dispute settlement body (DSB) -- long a target of attacks by Washington -- agreed last month with Canada's complaints that Washington had violated trade rules when imposing duties on lumber widely used in construction.  US Trade Representative (USTR) Robert Lighthizer had immediately slammed the decision as "erroneous" and said they "prevent the United States from taking legitimate action in response to Canada's pervasive subsidies ...