(Adds portfolio manager comment, updates prices to close)
* TSX ends down 20.27 points, or 0.13 percent, at 15,191.60
* Eight of the TSX's 10 main groups move lower
* Index rises 0.9 percent on the week
TORONTO, Sept 1 (Reuters) - Canada's main stock index slipped on Friday as retailers pulled back on investor fears about the threat posed to their business by Amazon's Whole Foods Market acquisition a day after the index hit a three-week high.
Empire Co Ltd, the parent company of the Sobeys and Foodland grocery chains, fell 4.7 percent to C$20.01, rival Loblaw Cos Ltd lost 3.5 percent to C$65.33, and Metro Inc was down 1 percent to C$40.82. The consumer staples group fell 1 percent overall.
Amazon is preparing to offer deliveries of groceries and other items within two hours in Vancouver starting in November and in Toronto from January, the Wall Street Journal reported late on Thursday, citing unnamed sources.
"That's a lot earlier than people were expecting," said Manash Goswami, portfolio manager at First Asset Investment Management.
The company has 13 Whole Foods Market stores in Canada, mostly in and around Toronto and Vancouver.
Rising energy stocks offset those losses even as oil prices held steady and gasoline slid for the first time since Hurricane Harvey hit the U.S. oil industry heartland, with Suncor Energy up 1 percent at C$39.51 and Canadian Natural Resources Ltd adding 0.7 percent to C$38.74.
The Toronto Stock Exchange's S&P/TSX composite index ended down 20.27 points, or 0.13 percent, at 15,191.60.
Eight of the index's 10 main groups were in negative territory, although decliners only outnumbered advancers by a 1.2-to-1 ratio overall.
The index notched a 0.9 percent gain on the week, buoyed by robust earnings reports from the country's biggest banks and evidence of rapid growth in the domestic economy.
"Given the strong GDP print, investors may be taking a wait-and-see approach to see what the Bank of Canada does. Maybe they raise this month and so people are being a little more cautious," Goswami said.
Perceived chances of a Bank of Canada interest rate hike next week rose on Friday to 50-50, the overnight index swaps market indicated.
The most influential gainers included Toronto-Dominion Bank , which extended gains from Thursday after reporting strong quarterly results. It was up 0.7 percent to C$67.50.
BRP Inc, the maker of Ski-Doo vehicles, fell 1.7 percent to C$40.81 despite reporting earnings and revenue that exceeded analysts' expectations.
Alaris Royalty Corp jumped 5.6 percent to C$21.96 after the financing company said it had funded a new partner and CIBC analysts raised their price target on the stock to C$23. (Reporting by Alastair Sharp; Editing by Jeffrey Benkoe and James Dalgleish)