* TSX falls 31.10 points, or 0.24 percent, to 12,813.96 * Nine of 10 main sectors decline * Index heads for weekly gain * Bullion climbs, lifting gold mining stocks By John Tilak TORONTO, Sept 6 (Reuters) - Canada's main stock index slipped on Friday after three straight sessions of gains as a disappointing U.S. jobs report showed weakness in the world's biggest economy, driving declines in almost every major sector. But the data also lessened fears of an immediate pullback in stimulus measures by the U.S. central bank. That lifted the price of bullion, which is seen as a safe-haven trade in the face of bad economic news, and gold-mining stocks by extension. U.S. job growth missed expectations in August and the unemployment rate hit a 4-1/2 year low as Americans gave up the search for work, complicating the U.S. Federal Reserve's decision on whether to begin trimming its bond buying later this month. Investors have been dissecting every piece of economic data to try to determine when the Fed will begin dialing back the asset purchases. The Fed meets later in the month to discuss monetary policy. "The advocates of a more accommodating policy are going to have more ammunition going into the meeting this month, to potentially postpone the timing of the taper," said Stephen Wood, chief market strategist, North America, at Russell Investments. "These data were soft enough to create a more dynamic position conversation at the next meeting," he added. "The certainty the market had about the September time frame for taper became less certain." The Toronto Stock Exchange's S&P/TSX composite index was down 31.10 points, or 0.24 percent, at 12,813.96, though it is still on track for a weekly gain. Nine of the 10 main sectors on the index were in the red. Financials, the index's most heavily weighted sector, slipped 0.2 percent. Royal Bank of Canada lost 0.2 percent C$66.41, and Bank of Montreal gave back 0.7 percent to C$67.11. Industrials stumbled 0.8 percent. Canadian Pacific Railway Ltd shed 1.8 percent to C$125.36, and Canadian National Railway Co fell 0.5 percent to C$100.33. Valeant Pharmaceuticals International Inc dropped almost 1 percent to $103.89, having the biggest negative influence on the market and dragging the healthcare sector down 0.8 percent. The lone gainer was the materials sector, which includes mining stocks. The group advanced 0.7 percent, with a 1.5 percent rise in the bullion price boosting gold producers. Goldcorp Inc added 0.8 percent to C$30.71, and Barrick Gold Corp gained 0.3 percent to C$20.01.