* TSX down 15.84 points, or 0.12 percent, at 13,098.55 * Investors await Federal Reserve meeting next week By Alastair Sharp TORONTO, Dec 13 (Reuters) - Canada's main stock index slipped slightly on Friday, with the decline led by heavyweight banking stocks and with shares of energy companies lagging as oil prices fell. Broad price action is expected to be muted in the session and through until the U.S. Federal Reserve holds its policy-setting meeting on Dec. 17 and 18. "It's going to be quiet until the Fed meeting next week," said Rick Hutcheon, president and chief operating officer at RKH Investments. The U.S. central bank is not expected to curtail its stimulus - which has helped push U.S. indices to record-highs - at this meeting, but Hutcheon said any surprise reduction in the amount of money the Fed is pumping into the financial system should be seen as a positive for the broader economy. "If they pull back and the market falls, it could be a buying opportunity," he said. Potash Corp gained 1.9 percent to C$32.98 after China's Sinochem announced a one-year renewal of its three-year exclusive potash deal with Canpotex, the Canadian potash association. The heaviest weights on the index were a mixed bag, with Canadian National Railway Co off 0.9 percent at C$57.88, Bank of Nova Scotia down 0.5 percent at C$62.65, and Suncor Energy Inc losing 0.8 percent to C$35.70. The price of Brent crude fell towards $108 a barrel, though the spread between Brent and U.S. oil has narrowed to the benefit of Canadian producers. Telecom companies also weighed, with Telus Corp slipping 1.4 percent to C$35.90 and BCE Inc down 0.8 percent at C$45.25. By mid-morning, the Toronto Stock Exchange's S&P/TSX composite index was trading down 15.84 points, or 0.12 percent, at 13,098.55.