CANADA STOCKS-TSX falls on U.S. political worries, metals decline

TORONTO, Aug 17 (Reuters) - Canada's main stock index retreated on Thursday for the third straight day, as U.S. political worries weighed on investor sentiment and some base-metal prices pulled back from multi-year highs.

The Toronto Stock Exchange's S&P/TSX composite index unofficially closed down 48.57 points, or 0.32 percent, at 15,033.64. Nine of the index's 10 main groups ended lower. (Reporting by Fergal Smith; Editing by Phil Berlowitz)