Copper resumed its decline on Wednesday as some speculators took profits from a December rally and others went short after prices broke below technical levels.Copper surged 12 percent during its December rally and has since eased back by about 3 percent.

"That was a pretty rapid rise in December and we seemed to have traded ahead of the fundamentals, so there was always the risk of profit-taking, given the net speculative positioning was elevated," said Robin Bhar, head of metals research at Societe Generale in London.Bhar added that once prices broke technical support levels that triggered more selling, though he said he viewed any further falls as a buying opportunity.

There is uncertainty about supply in the market because of Chinese import restrictions on copper scrap and labour contract talks at several mines, including the huge Escondida mine, Bhar said. Reuters