June 16 (Reuters) - Canada’s main stock index treaded water on Wednesday, tracking the Wall Street, as investors awaited comments from the U.S. Federal Reserve on when it would ease its monetary stimulus. * At 9:31 a.m. ET (1331 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 10.92 points, or 0.05%, at 20,242.24. (Reporting by Amal S in Bengaluru; Editing by Amy Caren Daniel) Our Standards: The Thomson Reuters Trust Principles.