TORONTO (Reuters) - Toronto's main stock index fell yesterday, snapping a two-session advance, as a decline in commodity prices erased an earlier rally that had lifted the resource-heavy index to its highest level in over 14 months.

Shares of EnCana Corp., which headlined the decline, ended down 4.4 percent at C$28.81. The slide came a day after EnCana completed its split into separate gas and oil businesses.

Talisman Energy shares fell 2.7 percent to C$18.42, while Nexen Inc. dropped 1.9 percent to C$25.26. The drag in energy shares came as the price of oil slipped on weak US service sector data and rising US crude inventories.

Also contributing to the broader decline was a slide by gold miners, which fell as the price gold backed away from a record high.

Shares of Barrick Gold Corp slid two percent to C$49.42, while Goldcorp fell 1.5 percent to C$47.48.

"We've had a nice little run here," said Irwin Michael, portfolio manager at ABC Funds.

"I can't pinpoint why, but the markets are becoming increasingly thin right now."

The S&P/TSX composite index finished down 143.18 points, or 1.22 percent, at 11,636.55. It is now up over 55 percent from the five-year low it had tumbled to in March.

The lower close marked a sharp turnaround from early in the session when initial strength in financials after some upbeat bank earnings helped power the TSX to a gain of 36 points and its highest level since September 2008.

Canadian Imperial Bank of Commerce and Toronto-Dominion Bank reported better than expected profits and offered signs that bad loans may have peaked. Bank executives said they were heading into 2010 primed for growth.

Shares of TD Bank fell 2.5 percent to C$66.08, while CIBC bucked the downtrend and rose 2.2 percent to C$70.