Canada's main stock index is expected to extend this year's hefty gains in 2017, a Reuters poll found, although stock market strategists said they are concerned about the outcome of the U.S. election and potential threats to global trade.

The Toronto S&P/TSX composite index has rallied nearly 28 per cent since hitting a three-year low in January as the price of oil, a key Canadian export, partially recovered.

But the TSX has traded mostly sideways since August, as investors weighed the risk of a Federal Reserve interest rate hike before year end, now most likely in December, and as the U.S. presidential election race has tightened in the polls.

"I worry the markets have totally mispriced political risk in the U.S.," said Colin Cieszynski, senior market analyst at CMC Markets Canada. He expects Canadian stocks to reach 14,750 by year end and 16,000 by end-2017.

A win for Republican U.S. presidential candidate Donald Trump would add to protectionism concerns which threaten global trade, Cieszynski added

Trump has said he would renegotiate or scrap the North American Free Trade Agreement if he is elected.

The median forecast from the Reuters poll of 25 strategists was for the TSX index to rise to 14,900 by the end of 2016, up over 1 per cent from Monday's close of 14,689.04 and 15 per cent above the 13,009.95 where it ended last year.

It fell just over 11 per cent in 2015.

A rise in oil prices after the Organization of the Petroleum Exporting Countries agreed to limit crude output improves the earnings outlook for Canada's many energy-linked companies, while low or negative bond yields boost the relative attractiveness of Canadian stocks.

Investors are being forced to participate in the stock market because there are no better alternatives, said Rick Hutcheon, president at RKH Investments.

The index is expected to rise to 15,400 by mid-2017 and to extend those gains to 15,775 by the end of next year.

Still, some investors worry corporate earnings will disappoint as the global and domestic economies struggle to grow.

Domestic economic risks include an over-leveraged consumer and a potential housing market bubble, said Elvis Picardo, vice president of research at Global Securities.

Canadian policymakers are facing increased pressure to support the country's lackluster economy as infrastructure spending takes time to kick in and record high debt loads dampen the impact of stimulus checks.

Other potential risks that worry investors are a slowdown in China and a spike in global bond yields.

"Bonds look overvalued ... and investors seem to be losing faith in central banks' ability to manage economic risks through (quantitative easing)," Picardo said.