As negotiators head into the third round of talks to modernize the North American Free Trade Agreement, an IPSOS poll published on Thursday showed broad-based support among Americans, Canadians and Mexicans for the 23-year trade pact.

Despite repeated attacks against NAFTA by U.S. President Donald Trump, the poll showed that 58 percent of American respondents overall, 79 percent of Mexicans and 74 percent of Canadians support their countries' participation in one of the world's biggest trading blocs.

NAFTA underpins over $1 trillion a year in trade between the three countries, accounting for 39 percent of Canada's GDP and 49 percent of Mexico's but just 5 percent in the case of the United States, the world's largest economy.

The next round of negotiations is scheduled to begin in Ottawa on Saturday.

A breakdown of the poll showed that just 27 percent of U.S. respondents between the ages 18 and 35 "strongly support" NAFTA, however, while only 16 percent of Americans 55 years and older strongly support being part of the trade agreement.

Some 21 percent of younger Americans believe they have personally benefitted from trade under NAFTA compared to 10 percent of older Americans, the poll said.

It also showed that Americans overall were substantially less likely than Canadians or Mexicans to say free trade has helped their country.

About 35 percent of Americans believe Mexico has benefitted the most from NAFTA, according to the poll. That compares with 64 percent of Mexicans and 34 percent of Canadians who believe the United States has gained the most from the agreement.

When it comes to renegotiating NAFTA, some 48 percent of Americans and 46 percent of Mexicans said they believed it was a good thing. But just 33 percent of Canadian respondents said revamping the treaty was a good step.

A separate Reuters poll of economists showed on Thursday that the Mexican and Canadian economies should survive current NAFTA talks relatively unscathed.

The economists said concerns about damage from the renegotiation may be overblown, with the most likely result of the talks being an updated trilateral agreement after many months or years.

In the IPSOS poll, some 59 percent of Canadians said they were confident in their government's ability to renegotiate NAFTA in Canada's best interest. That compared with the 50 percent of Americans who said they were confident in the Trump administration's ability to negotiate in their country's best interest.

Mexicans were more wary, with just 40 percent voicing confidence in their government's ability to negotiate.

If negotiations fail, 50 percent of Americans, 59 percent of Canadians and 60 percent of Mexicans said they would prefer that NAFTA continue in its current form.

This article was provided by Reuters.