*TSX falls 20.33 points to 12,214.18
*Materials, energy, financial groups lower (Updates with details, commentary)
By Claire Sibonney
TORONTO, Sept 21 (Reuters) - Toronto's main stock index lost steam on Tuesday morning as commodity prices softened and investors were hesitant to place big bets ahead of the U.S. Federal Reserve's policy meeting later in the day.
Oil, copper and gold prices all eased but remained supported by some speculation that the Fed may signal a move towards further stimulus measures.
The index's materials sector slipped 0.8 percent and energy stocks fell 0.2 percent.
Among the biggest decliners, Barrick Gold Corp (ABX.TO) -- which rallied on Monday as gold hit record highs -- fell 1.5 percent to C$47.09, and Teck Resources TCKb.TO dropped 0.8 percent to C$38.78.
"You've just got a little consolidating profit-taking here on the opening ... the market had a good day yesterday," said Bruce Latimer, trader at Dundee Securities.
The Fed is expected to restate its existing policy with no fresh stimulus and interest rates kept at almost zero but is coming under increasing pressure to inject more money into the sluggish U.S. economy. [ID:nSGE68J04M]
"I think that's already baked into the market," Latimer said. "I don't think people are expecting any fireworks out of the meeting today."
At 10:07 a.m. (1407 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 20.33 points, or 0.17 percent, at 12,214.18. But only three of its 10 sectors were lower, including heavyweight financials, which were off 0.1 percent.
On Monday, the TSX finished at its highest closing level since April.
Also tugging the TSX down, Potash Corp (POT.TO) fell 0.2 percent to C$152.28 after BHP Billiton's (BHP.AX) $39 billion battle to take control of the world's largest fertilizer maker failed to win immediate backing from Canadian authorities. [ID:nLDE68K038]
On the upside, Research In Motion RIM.TO gained almost 2 percent to C$47.25 after a senior Indian government source told Reuters the government is in talks with the company for access to BlackBerry corporate emails. [ID:nSGE68K0JU]
($1=$1.03 Canadian) (Reporting by Claire Sibonney; editing by Peter Galloway)