The market also processed figures showing a bigger-than-expected drop in the number of Americans filing new claims for unemployment benefits last week.

Further, separate surveys indicated a slowdown in business growth in China and the euro zone.

Yellen is expected to address policymakers at an annual meeting of central bankers and economists in Jackson Hole, Wyoming that is underway.

The benchmark TSX, which hit a record high in the previous session, is up about 14 percent this year. Some investors say those gains could be followed by a pullback.

“The market will be choppy until it has a correction. I think there's more downside than upside,” said David Cockfield, managing director and portfolio manager at Northland Wealth Management.

“I’m not long-term bearish, but I’m certainly short-term bearish," he added. "(Fundamentals) are okay, it’s just that we need a little shakeout."

The Toronto Stock Exchange's S&P/TSX composite index was down 5.86 points, or 0.04 percent, at 15,556.09. Seven of the 10 main sectors on the index were in the red.

Financials, the index's most heavily weighted sector, climbed 0.6 percent, with Bank of Nova Scotia rising 0.4 percent to C$73.80 and Toronto Dominion Bank adding 0.6 percent to C$57.90.

Shares of energy producers received a lift from higher crude oil prices. Suncor Energy Inc was up 0.2 percent at C$43.75, and Canadian Natural Resources Ltd advanced 0.6 percent to $46.43.

The gold-mining sector dropped with the bullion price. Goldcorp Inc shed 3.5 percent to C$30.05 and Barrick Gold Corp declined 1.8 percent to C$20.18.

(Editing by Bernadette Baum and Meredith Mazzilli)

By John Tilak