Prime Minister Stephen Harper issued a friendly warning to Democratic presidential hopefuls south of the border on Thursday, saying it would be a "mistake" for the United States to reopen the North American Free Trade Agreement.

Prime Minister Stephen Harper says he "highly doubts" a future U.S. president would reopen the North American Free Trade Agreement.
(Fred Chartrand/Canadian Press)

His comments, during Thursday's question period in the House of Commons, came two days after presidential hopefuls Hillary Clinton and Barack Obama threatened to pull the U.S. out of the 15-year-old free trade agreement with Canada and Mexico unless it's renegotiated.

"If any American government ever chose to make the mistake of opening that, we would have something we would want to talk about as well," the prime minister said with a smile, in response to a question from NDP Leader Jack Layton.

He didn't elaborate, but earlier this week, Trade Minister David Emerson and Finance Minister Jim Flaherty said U.S. officials should not forget the benefits of the agreement and hinted Canada could respond to a NAFTA pull-out by renegotiating U.S. access to Canada's oil.

Layton urged Harper to take advantage of the opening and negotiate better labour and environmental standards.

But Harper added he "highly doubts" a new president would take such a step.

Clinton vows to renegotiate on U.S. terms

Clinton was asked in Tuesday's Democratic debate whether she would notify Canada and Mexico that the U.S. would pull out of NAFTA within six months of her presidency.

"No. I will say, we will opt out of NAFTA unless we renegotiate it," Clinton said. "And we renegotiate it on terms that are favourable to all of America."

Democratic presidential hopeful Hillary Rodham Clinton, left, listens as her rival, Barack Obama, responds to a question during a Democratic presidential debate on Tuesday in Ohio.
(Mark Duncan/Associated Press)

Clinton said her demands would include tougher enforcement of labour and environmental standards, adding that she would take out the ability of foreign companies to sue the U.S. over its protection of workers.

Obama said he agreed with Clinton's criticisms of the deal, and added he would use the "hammer" of a potential opt-out as "leverage to ensure that we actually get labour and environmental standards that are enforced."

"I will make sure that we renegotiate in the same way that Senator Clinton talked about, and I think actually Senator Clinton's answer on this one is right," he said during the debate.

Democrats have long blamed the trade deal between Canada, the U.S. and Mexico for job losses in states such as Ohio, where the latest Democratic primary is taking place next Tuesday.

With files from the Canadian Press