OTTAWA -- A growing number of Canadian exporters were saying the NAFTA talks were having a negative impact on their operations even before the trade dispute with the United States escalated in recent weeks.

A survey done for Export Development Canada found 28 per cent of the 1,000 exporters polled said the NAFTA talks had a negative impact on their Canadian operations.

That was up from 23 per cent in an earlier survey.

"Current sales may be riding high, but trade uncertainty is having an impact," EDC chief economist Peter Hall said in a statement Friday.

"Nearly one in five exporters say that NAFTA talks have negatively affected their investment plans. This reluctance to invest could severely restrain Canada's export capacity in the years ahead."

The survey was done from April 18 to May 11, before the United States ended an exemption for Canada on the global steel and aluminium tariffs it had put in place in March.

Since the tariffs went into place on Canadian metal exports at the end of May, Canada has imposed retaliatory tariffs on steel and aluminium coming from the U.S. as well as a wide range of consumer goods, while the U.S. has threatened additional tariffs on the auto sector.

The bi-annual survey found overall trade confidence increased to 76.5 per cent from 73.5 per cent in the previous questionnaire which was done at the end of last year.

The increase came as 73 per cent of Canadian companies indicated their export sales will increase over the next six months compared with 56 per cent in the previous survey.

More businesses said their sales to the U.S. increased over the past six months with 46 per cent reporting an increase compared with 36 per cent.

The EDC survey also noted that rising interest rates were having a negative impact on the sales of a larger share of exporters at 30 per cent compared with 21 per cent in the previous survey.

The Bank of Canada raised its key interest rate target to 1.5 per cent this week, prompting Canada's big banks to raise their prime lending rates.

In raising the rate, the central bank said that despite the trade dispute it still projects Canadian growth to average just slightly above its potential with inflation already on target.

It expects the downside of the trade policies to be largely offset by higher oil prices and the stronger U.S. economy.