* TSX falls 99.70 points, or 0.74 percent, to 13,319.87 * Seven of 10 main index sectors decline * BMO slips 4.5 percent, weighs most on market * Potash up after announcing job cuts By John Tilak TORONTO, Dec 3 (Reuters) - Canada's main stock index fell on Tuesday to its lowest in more than five weeks after Bank of Montreal's quarterly results disappointed investors, spurring a selloff that spread to the shares of other major banks. BMO, the country's No. 4 bank and the first of the big lenders to report earnings, gave back 4.5 percent, to C$70.25, and had the biggest negative influence on the market. Also weighing on sentiment, recent positive economic data out of the United States, including upbeat manufacturing numbers on Monday, revived fears the U.S. Federal Reserve might begin a scale-back, or tapering, of its monetary stimulus program sooner than later. The Toronto stock market snapped a four-session run of gains on Tuesday. In each of the past five months, the benchmark TSX index has advanced. "We still have the cloud of tapering hovering over the economy and the markets," said Paul Taylor, chief investment officer at BMO Asset Management. "And no doubt when we get the taper, it will be a cause for some short term negative sentiment and volatility." The Toronto Stock Exchange's S&P/TSX composite index closed down 99.70 points, or 0.74 percent, at 13,319.87, after touching 13,279.08, its lowest since Oct. 24. Taylor expects the resource-focused Canadian market to end 2014 higher, but noted that significant headwinds remained. "We're still struggling with relatively weak commodity prices, and our exports sector is not delivering in a meaningful way enough to bolster stronger economic growth," he said. Seven of the 10 main sectors on the index were in the red on Tuesday. The financial sector gave back 1.6 percent. Royal Bank of Canada fell 1.3 percent to C$69.56, and Toronto Dominion Bank was down 0.8 percent at C$96.13. BMO's fourth-quarter earnings rose 1 percent due to stronger wealth management profit, but the stock was pulled down by the sluggish performance of its U.S. Harris Bank unit. The bank also raised its dividend. "The important thing to look at is that BMO increased their dividend and they're doing a share buyback," said Stan Wong, vice president and portfolio manager at Richardson GMP Limited. "I'm pretty constructive on the banks," added Wong, whose portfolio includes RBC and Bank of Nova Scotia. "The banks can benefit from an improving economy and the fact that investors are looking for visible yields that are also growing." Despite a slightly higher bullion price, gold-mining shares slipped 1.4 percent. Goldcorp Inc lost 2.2 percent to C$22.25 and Barrick Gold Corp declined 0.2 percent to C$16.51. In other news, Potash Corp of Saskatchewan Inc said it will cut its workforce by 18 percent as it struggles with slumping demand and weak prices for the crop nutrient. The stock rose 0.3 percent to C$33.82.