Oct 27 (Reuters) - Toronto's resource-heavy main stock index fell at the open on Wednesday as mounting doubts about the size and timing of U.S. economic stimulus measures pushed up the U.S. dollar and weighed on commodity prices.
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE opened down 4.14 points, or 0.03 percent, at 12,680.54, before extending losses. (Reporting by Claire Sibonney; editing by Peter Galloway)
