Canada's main stock index fell more than 300 points Wednesday amid a broad-based decline, while U.S. markets also slid. 

Fitch Ratings cut the U.S. government’s credit rating from AAA to AA+ and that news was the focus for Wednesday, said Anish Chopra, managing director with Portfolio Management Corp. 

“It's really the Fitch news today that's dominating the market,” he said. 

Among Fitch’s concerns were the growing debt-to-GDP ratio, said Chopra, as well as rising fiscal deficits and higher debt repayment costs due to interest rate hikes. 

Investors are reacting by pulling back in one of the more risk-off days the markets have seen in a while, he said. 

It was one of the worst days in months for Wall Street after a months-long rally appeared to lose its steam Wednesday. In New York, the Dow Jones Industrial Average was down 348.16 points, or almost one per cent, at 35,282.52. The S&P 500 Index was down 63.34 points, or almost 1.4 per cent, at 4,513.39, while the Nasdaq Composite was down 310.47 points, or more than two per cent, at 13,973.45.

The S&P/TSX Composite Index closed down 314.72 points, or 1.53 per cent, at 20,218.21.

Meanwhile, second-quarter earnings season continued in the background. Around two thirds of the companies that make up the S&P 500 have reported so far, with around 80 per cent reporting earnings above analysts’ expectations, said Chopra.

“On the earnings front, companies are doing reasonably well,” he said. 

However, a report from ADP released Wednesday showed private-sector hiring may be stronger than expected, which could feed into fears about interest rates remaining higher for longer, said Chopra. 

Friday will see the latest jobs report from the U.S. government, a key factor in the Federal Reserve’s next interest rate decision in September. 

“There’s the possibility ... that the employment story in the United States is still strong,” said Chopra. 

Major tech stocks helped pull U.S. markets lower, as technology and other high-growth stocks tend to be more sensitive to interest rate news. 

The Canadian dollar traded for 74.99 cents U.S. compared with 75.24 cents U.S. on Tuesday.

The risk-off sentiment was seen across sectors, with commodities also slumping as concern about China’s economy also weighed on the markets, said Chopra.

The September crude oil contract was down US$1.88 at US$79.49 per barrel and the September natural gas contract was down eight cents at US$2.48 per mm/BTU.

The December gold contract was down US$3.80 at US$1975.00 an ounce and the September copper contract was down seven cents at US$3.84 a pound.