TORONTO (Reuters) - Toronto's main stock index ended down slightly yesterday, pulling back from an 18-month high as initial optimism over a Greek debt deal faded, while retreating metal prices pulled down mining issues.

The index charged to its highest level since September 2008 early in the session, after euro zone finance ministers agreed on a 30 billion euro ($40.5 billion) rescue package for Greece.

But after going as high as 12,214.39, the TSX pulled back following cautionary comments from the German finance ministry and a late retreat in gold and base metals prices.

"The Greece debt story put a bid under the market...but on the day we're seeing the commodity stocks a little bit weak," said Elvis Picardo, strategist at Global Securities in Vancouver.

"I'm not seeing too much conviction one way or the other."

The Toronto Stock Exchange's S&P/TSX composite index ended down 28.18 points, or 0.22 percent, at 12,148.66.

Materials issues fell by one percent, led by retreating gold producers.

Iamgold eased 2.6 percent to C$15.39, while Centerra Gold slid 2.4 percent to C$11.15.

Overall, half of the TSX's 10 main groups finished lower on the day.

Canadian Oil Sands Trust which owns 37 percent of the huge Syncrude oil sands project, surged five percent to C$32.22 after Chinese state-owned company Sinopec agreed to buy a nine percent stake in the project from CononcoPhillips for $4.65 billion.

But as a group, TSX energy stocks fell 0.2 percent on weaker crude oil prices.