(Repeats to add dropped letter to word "MARKETS" in slug)
* TSX down 99.99 points at 11,649.13
* Banking shares lead index lower
* Eight of the index's 10 main groups down (Recasts, updates prices, adds details, quotes)
By Claire Sibonney
TORONTO, May 28 (Reuters) - Toronto's main stock index extended losses on Friday afternoon as weak U.S. economic data undermined confidence in recovery and as investors moved to the sidelines ahead of a long weekend in the United States.
Data showed U.S. consumer spending was unexpectedly flat last month and growth in business activity in the Midwest slowed.
That drove down U.S. stock markets, and commodity prices, including key Canadian exports oil, gold and copper, eased. [O/R] [GOL/] [MET/L]
"We're heading into a long weekend, with U.S. markets closed on Monday, and we've got a very choppy and fragile market," said Barry Schwartz, vice president and portfolio manager at Baskin Financial Services.
Monday is the Memorial Day holiday in the United States.
"If there's any bad news out of Spain or Korea, or anywhere in the euro zone (over the three-day weekend), then people don't want to be locked into stocks."
Heavyweight names on the downside included Royal Bank of Canada (RY.TO), which dropped 2.8 percent to C$55.26. Barrick Gold Corp (ABX.TO) was off more than 1 percent at C$44.10, and Teck Resources TCKb.TO slid 2.5 percent to C$35.87.
Among the gainers, Cenovus Energy (CVE.N) added 1.6 percent to C$26.95, and Canadian Natural Resources (CNQ.TO) rose 0.5 percent to C$36.66.
At 12:45 p.m., (1645 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 99.99 points, or 0.85 percent, at 11,649.13, with eight of its 10 main groups lower.
"All in, a real brutal month of May. The sooner we can get it closed the better," Schwartz said.
The TSX opened higher, supported by strength in energy shares and global stocks, but eventually it slid decidedly lower in line with U.S. equities.
($1=$1.05 Canadian) (Editing by Peter Galloway)