The S&P/TSX composite index weakened 93.17 points to close at 11,664.71, with most of the decline coming in afternoon trading. The TSX Venture Exchange slipped 1.35 points to 1,183.01.
The Canadian dollar fell 0.11 of a cent to 99.71 cents US.
Hopes began to fade over how much the European Central Bank will do to help countries with crippling debt when it meets on Thursday.
Meanwhile, the Federal Reserve has started its two-day policy meeting, and is expected to announce some kind of new step to energize the U.S. economy, though the timing is still in question.
Some economists have suggested that the Fed isn't convinced that the U.S. economic slowdown is in such a state to warrant further economic stimulus — and recent economic data has shown some positive elements.
"If the Fed and the ECB don't do anything, as some economists expect, it's going to be quite disappointing for investors," said John Johnston, chief strategist at David Rea Ltd. in an interview.
"If they just barely meet expectations by doing something typical and not overly aggressive then I think the equity markets are vulnerable to some profit taking."
In U.S. economic data, consumer confidence rose in July for the first time in four months. The Conference Board said the confidence index increased to 65.9, from 62.7 in June. That's the highest reading since April and better than the reading of 62 that economists had forecast.
However, the index sits notably lower than 90, which indicates a healthy economy.
Also, U.S. home prices rose in May from April in every city tracked by a leading index, a sign that increasing sales and tight inventories are supporting a modest housing recovery. The Standard & Poor's/Case-Shiller home price index showed a measure of national prices rose 2.2 per cent from April to May, the second increase after seven months of flat or declining readings.
On Wall Street, the Dow Jones industrial average declined 64.33 points to 13,008.68 and the Nasdaq was down 6.32 points at 2,939.52. The S&P fell back 5.98 points to 1,379.32.
In commodities, the September crude contract on the New York Mercantile Exchange was down $1.72 to US$88.06 a barrel near midday. Earlier in the session, crude had been above Monday's close.
September copper moved up 1.5 cents to US$3.42 a pound while August gold ended off $9.20 at US$1,610.50 an ounce.
In corporate developments, Rona Inc. (TSX:RON) shares were up 13.7 per cent after the company rebuffed an unsolicited takeover from Lowe's Companies worth $1.76 billion. The Montreal-area company said the offer from its American rival (NYSE:LOW) wouldn't be in its shareholders' best interest, but Lowe's said it intended to further pursue a transaction. Rona shares rose $1.63 to $13.50.
In earnings news, Thomson Reuters (TSX:TRI) says its adjusted profit rose to 54 cents per share, compared to 51 cents per share in the second quarter of 2011. Its diluted earnings per share, under IFRS, was $1.11 per share up from 67 cents per share in the second quarter of 2011. Overall revenue fell by four per cent to US$3.3 billion from $3.4 billion. Shares backed off 50 cents to $28.44.
Inmet Mining (TSX:IMN) said higher copper sales volumes helped push its second quarter earnings up 74 per cent from profits reported a year earlier. The company reported net income of US$94.2 million or $1.36 per share for the quarter ended June 30, compared to $54.3 million or 83 cents per share for the same period a year earlier. Inmet shares gained five per cent, or $1.81 to $39.89.
A federal arbitrator has sided with Air Canada (TSX:AC.B) in its labour dispute with the union representing its pilots. The five-year collective agreement will be effective until April 2016, and would, among other things, include provisions allowing the airline to create a budget carrier. Shares were up six cents, to $1.14.
Canadian cheese and dairy giant Saputo (TSX:SAP) saw profits fall four per cent in the latest reported quarter, affected by lower cheese prices in the U.S. and an inventory writedown. The company posted earnings of $121.8 million, off from $126.6 million a year ago. Revenue came in at $1.7 billion, up nearly four per cent year over year. Shares of the company dropped $1.34 to $42.73.
George Weston Ltd. (TSX:WN) says it expects full-year 2012 results will be lower than last year, mainly due to costs at its Loblaw (TSX:L) grocery division. The bakery and grocery company said second-quarter profits dropped 15 per cent to $196 million, of which $137 million was attributable to common shareholders. Overall revenue increased 1.3 per cent to $7.6 billion. Its shares fell 59 cents to $59.25.
Toromont Industries Ltd. (TSX:TIH) says its second-quarter profit from continuing operations was $25.7 million, an improvement from the comparable period last year when it earned $159.7 million. The profit amounted to 34 cents per share, two cents per share below a consensus estimate compiled by Thomson Reuters. Toromont shares were down 10 cents to $20.85.