(Adds investor quotes and details throughout, updates prices) * TSX ends down 0.4% * The materials group falls nearly 3% * Energy ends 0.9% lower * Gold and copper prices slide TORONTO, Sept 16 (Reuters) - Canada’s main stock index fell on Thursday, led by declines for mining shares, as investors weighed prospects of the Federal Reserve dialing back its huge stimulus and awaited the outcome of next week’s federal election. The Toronto Stock Exchange’s S&P/TSX composite index ended down 91.69 points, or 0.4%, at 20,602.10. “There’s probably some more nervousness about tapering,” said Matt Skipp, president of SW8 Asset Management, who was nonetheless doubtful that the Federal Reserve would for now “say anything to surprise the markets.” Increased focus on the timing of the Fed’s asset purchase reduction came as data showed U.S. retail sales unexpectedly increasing in August. The Fed is due to make an interest rate decision next week. U.S. government bond yields and the U.S. dollar rose, while base and precious metal prices fell, with gold down 2.2% and copper sliding 3.2%.The materials group, which includes precious and base metals miners and fertilizer companies, lost nearly 3%. Energy ended 0.9% lower. Foreign investors are growing more worried that Canada’s federal election on Monday could result in a deadlock that hampers Ottawa’s response to the COVID-19 pandemic and further slows the economic recovery from the crisis. Another concern for investors is rising inflation, with data on Wednesday showing that Canadian inflation has accelerated to its highest level since March 2003. Still, the Bank of Canada expects inflation to cool as temporary factors pushing up prices fade. “If inflation comes with subdued interest rates, it’s good for Canadian stocks, it’s good for commodity prices,” Skipp said. The TSX has advanced about 18% this year. (Reporting by Fergal Smith; Additional reporting by Amal S in Bengaluru; Editing by Peter Cooney)