At 10:27 a.m. ET (1427 GMT), the Toronto Stock Exchange's S&P/TSX composite index was up 3.20 points, or 0.03 percent, at 16,053.37.

The energy sector dropped 0.2 percent as US crude prices were down 1.5 percent a barrel.

The financials sector slipped 0.1 percent. The industrials sector rose 0.2 percent.

The United States said it was moving ahead with tariffs on aluminum and steel imports from Canada, Mexico and the European Union, ending a two-month exemption and potentially setting the stage for a trade war with some of America's top allies.

On the TSX, 102 issues were higher, while 139 issues declined for a 1.36-to-1 ratio to the downside, with 36.55 million shares traded.

The largest percentage gainer on the TSX was BRP Inc , which jumped 6.9 percent after first-quarter results.

Superior Plus fell 5.3 percent, the most on the TSX, after news of the company buying NGL Energy Partner's retail propane business. The second biggest decliner was Descartes Systems, down 5.1 percent after first-quarter results.

The most heavily traded shares by volume were Nemaska Lithium, Bombardier, and Green Organic Dutchman Holdings.

The TSX posted eight new 52-week highs and one new low.

Across all Canadian issues there were 20 new 52-week highs and four new lows, with total volume of 62.62 million shares.

Economic data showed that Canada's economy grew at its slowest pace in nearly two years in the first quarter amid cooler exports and a weaker housing sector, though growth was still seen as strong enough for the central bank to raise interest rates again.