* TSX down 157.69 points, or 1.29 percent, at 12,038.82
* Energy, materials sectors lead TSX slide
* Suncor up 0.4 percent after results (Updates figures, adds earnings result)
By Jennifer Kwan
TORONTO, May 4 (Reuters) - Toronto's main stock index fell hard on Tuesday morning as worries about the effectiveness of Greece's aid package intensified, sending investors scampering to the safety of the U.S. dollar and hitting oil and metals prices.
The index's heavily weighted energy sector dropped 1.6 percent, with EnCana Corp ECA.TO down 1 percent at C$33.15, and Canadian Natural Resources CNQ.TO retreating 3 percent to C$76.64.
Miner Teck Resources TCKb.TO slid 3.3 percent to C$37.51, while First Quantum Minerals FM.TO fell 4.3 percent to C$70.75, which weighed on the index's materials group.
"We are down on the Greek concerns. Commodities are super weak," said Francis Campeau, broker at MF Global Canada in Montreal.
At 10:56 a.m. (1456 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 157.69 points, or 1.29 percent, at 12,038.82.
The Toronto index took its cue from overseas stock markets, which dropped as investors remained skeptical that a weekend agreement among European countries and the International Monetary Fund to bail Greece out of its debt problems would succeed. [MKTS/GLOB] [.N]
The euro retreated against the greenback on fears that Greece's woes would spread to other vulnerable euro zone countries. [FRX/]
That concern guided investors toward the safety of the U.S. dollar, which pressured the price of oil below $84 a barrel, while base metals were also knocked lower on worries China would step up its credit tightening campaign. [O/R] [MET/] [ID:nTOE64100Q]
Financials fell 1.4 percent with Canada's biggest lender, Royal Bank of Canada RY.TO, down 1 percent at C$61.80.
Although lower, the TSX index was holding its ground compared with European equity markets, with some of then dropping more than 2 percent.
Shares of Suncor Energy Inc SU.TO, Canada's top energy company, climbed 0.4 percent to C$34.83 after it reported a quarterly profit that beat market expectations, helped by additional production from its acquisition of Petro-Canada and higher crude oil prices. [ID:nN03213638]
News and data provider Thomson Reuters Corp TRI.TO TRI.N reported a stronger-than-expected quarterly profit as the recovery from the financial crisis accelerated in its main businesses. Thomson Reuters shares were up 0.6 percent at C$37.00. [ID:nN03214917]
($1=$1.02 Canadian) (Reporting by Jennifer Kwan; editing by Peter Galloway)