* C$ at C$1.0311 vs US$ or 96.98 U.S. cents * Canadian bond prices lower By Leah Schnurr TORONTO, Sept 18 (Reuters) - The Canadian weakened slightly on Wednesday as investors were wary of placing aggressive bets ahead of a widely expected announcement from the U.S. central bank that it will begin scaling down its economic stimulus program. Before the statement from the Federal Reserve due in the afternoon, markets will be watching a speech from Bank of Canada Governor Stephen Poloz, which is expected to focus on economic growth in Canada. Following that, focus will turn south of the border with investors anticipating the Fed will begin slowly withdrawing its asset purchase program. The central bank is currently buying $85 billion in bonds a month to prop up the economic recovery and most analysts expect that will be reduced by a relatively small $10 billion. "The U.S. dollar has sold off fairly heavily over the past two weeks, and pretty much all of that has to do with reduced expectations on how much the Fed is going to pull back on the asset purchase program," said Greg Moore, FX strategist at Toronto-Dominion Bank. "Just given how far we've come since the beginning of the month, the Fed would have to sound fairly dovish in order to extend this move lower for dollar-Canadian dollar." The Canadian dollar was at C$1.0311 to the U.S. dollar, or 96.98 U.S. cents, weaker than Tuesday's session close of C$1.0295, or 97.13 U.S. cents. The Fed announcement is expected at 2 p.m. EDT (1800 GMT), followed by a press conference. Poloz is scheduled to give a speech in the morning on "the preconditions for a return to natural growth for Canada." "They may be addressing the lack of rotation to export-driven growth that they've been anticipating for quite some time now," said Moore. "So there could be some potentially Canadian dollar negative comments, especially if they're a little bit more downbeat on their outlook." Prices for Canadian government bonds were lower across the maturity curve, with the two-year bond down 3 Canadian cents to yield 1.278 percent, and the benchmark 10-year bond down 20 Canadian cents to yield 2.798 percent.