Sept 28 (Reuters) - Canada's main stock index slipped at the open on Friday, as investors assessed data showing stronger-than-expected domestic economic growth and ahead of an expected U.S.-Mexico trade agreement that will exclude Canada.
* At 9:33 a.m. ET (13:33 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 45.94 points, or 0.28 percent, at 16,158.68.