* TSX falls 0.4 percent to 12,599.23
* Eight of 10 main sectors decline
* Potash Corp rises as Saskatchewan rejects BHP's bid (Adds details)
TORONTO, Oct 21 (Reuters) - Toronto's main stock index fell on Thursday, led by a selloff in commodity prices, as investors fretted about the sluggish pace of the U.S. recovery, despite another round of strong U.S. corporate earnings.
U.S. dollar-denominated commodity prices extended declines, namely gold and crude oil, accelerated by a rebound in the U.S. greenback, and sent the TSX's materials group down 0.91 percent and the energy sector off 0.62 percent.
"It's not surprising, given that both those commodities are off quite significantly," said Elvis Picardo, analyst and strategist at Global Securities in Vancouver, said of the TSX's retreat.
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE closed down 50.69 points, or 0.4 percent, at 12,599.23. Eight of its 10 main groups fell.
Key decliners included Suncor Energy (SU.TO), down 1.8 percent at C$33.66, and Kinross Gold (K.TO), which shed 3.39 percent to C$17.96.
Toronto-Dominion Bank (TD.TO) fell almost 1 percent to C$75.28, while Encana (ECA.TO) dropped 2.64 percent to C$28.36.
The index has been trading sideways in recent sessions, after gaining around 10 percent since late August, and has not been far off its two-year high reached last week.
"It looks like the market is waiting for the other shoe to drop in terms of at least a modest correction. I think the overall sentiment is still quite good, but I think at the back of investors' minds there's this thing about October always being a rocky month," said Picardo.
Potash Corp (POT.TO) rose 0.5 percent to C$146.68 after the province of Saskatchewan, home base for the world's biggest fertilizer producer, said it was opposed to the $39 billion takeover bid by BHP Billiton (BHP.AX).
Saskatchewan Premier Brad Wall said the province will urge the federal government to block the Anglo-Australian miner's hostile bid. [ID:nN22340110] (Reporting by Ka Yan Ng; editing by Rob Wilson)