TORONTO -- Canada's main stock index headed lower Thursday as American stocks dropped sharply on news that U.S. President Donald Trump's tax cut plans may be delayed.

The S&P/TSX composite index was down 23.26 points to 16,082.09 in a broad-based decline that saw most major sectors finish in the red.

South of the border, cautious investors initiated a sell-off, with technology and industrial companies taking the biggest losses, after Senate Republicans surprised Wall Street by proposing a delay in cutting corporate taxes.

Senate Republicans are rolling out their own tax bill, which would delay the corporate tax rate cut until 2019, instead of 2018 under the House bill. Both bills would lower that rate to 20 per cent from 35 per cent. Postponing the tax cut would reduce the costs of the bill, which is projected to add more than US$1 trillion to the U.S. debt.

The Dow Jones industrial average was down 101.42 points to 23,461.94, after falling as much as 253 points earlier in the session.

The S&P 500 index was down 9.76 points to 2,584.62 and the Nasdaq composite index was down 39.07 points to 6,750.05.

"Wall Street's slumping basically on a fear about Trump's tax cut plan. That's weighing on things," said Jillian Bryan, vice-president at TD Wealth Private Investment Advice.

"Really, he's been ineffectual at getting any changes across at all so far if you look at health care and now these proposed tax changes."

In Canadian corporate news, mining company Cameco Corp. (TSX:CCO) saw its shares increase 2.96 per cent to $11.84 at the closing of markets Thursday. The movement follows its announcement Wednesday that it will temporarily suspend operations at its McArthur River mine and Key Lake milling operation by the end of January because of low uranium prices.

Meanwhile, shares of Eldorado Gold Corp. (TSX:ELD) moved up 3.87 per cent to $1.61 after the miner said it is suspending work at its Skouries development project amid its ongoing dispute with the Greek government.

On the energy front, pipeline giant TransCanada Corp.'s (TSX:TRP) stock dipped 0.29 per cent to $61.75 after it reported revenue fell to $3.24 billion compared with $3.63 billion in the same quarter last year.

In commodities, the December crude contract added 36 cents to US$57.17 per barrel and the December natural gas contract was up three cents to US$3.20 per mmBTU.

The December gold contract gained $3.80 to US$1,287.50 an ounce and the December copper contract was down a penny at US$3.09 a pound.

In currency markets, the Canadian dollar strengthened against a weakening greenback, trading at an average price of 78.79 cents US, up 0.23 of a U.S. cent.

With files from The Associated Press.