Trade representatives met in Vancouver Monday to discuss the North American Free Trade Agreement, just a week after U.S. presidential hopefuls took turns slamming the agreement on the election hustings.

The so-called NAFTA Commission — U.S. Trade Representative Susan Schwab, Mexico's Secretary of the Economy Eduardo Sojo and International Trade Minister David Emerson — began two days of discussions on Monday.

They were scheduled to hold a wrap-up news conference Tuesday, but had otherwise been staying out of the media spotlight.

However, NAFTA has been coming under fire in the presidential race.

The leading Democratic hopefuls all slammed the 1993 agreement during a labour-sponsored debate last week, calling for its reopening to entrench environmental and labour standards.

Senator Hillary Clinton, whose husband as president pushed NAFTA through Congress, declared the agreement had hurt American workers.

Rival Senator Barak Obama said if he won the 2008 vote he'd call "the president of Mexico, the president of Canada" to amend NAFTA to incorporate labour agreements.

Senator John Edwards, trailing the front-runners, has talked even tougher, but stopped short of calling for NAFTA to be scrapped.

Liberal trade critic Navdeep Bains said he's not surprised at the comments.

"People see an economic crisis on the horizon," said Bains, referring to the ballooning U.S. trade deficit, the deepening mortgage crisis and housing slowdown.

"I think there seems to be a knee-jerk reaction towards protectionism. The debates are a reflection of some of the concern that's been highlighted."

Veteran observers of the trade file tend to agree.

American unions and the Democratic party's left wing are generally anti-free trade but represent an important slice of the voter base for any presidential candidate, says Sidney Weintraub of the Washington-based Center for Strategic and International Studies.

But the eventual Democratic nominee is likely to follow tradition and move to a more moderate position, Weintraub said in an interview.

"I think it doesn't have too much traction," he said.

But an antitrade position can pay off in the presidential primary elections that determine each party's nominee, said Prof. James Brander of the University of British Columbia's Sauder School of Business.

There aren't many people likely to vote for candidates favouring trade liberalization, said Brander.

"And there are a lot of people, especially on the left, who are unhappy about NAFTA and about trade liberalization, who will vote for a candidate who takes a strong position on that," he said.

An antitrade position can pay off more in the primaries, which draw more actively partisan voters than the general election itself, said Brander.

The danger, said Weintraub, is if candidates find themselves locked into commitments they make during the primaries.

Republican candidates are generally antiprotectionist, but from their underdog position going into 2008 are unlikely to stump for more liberalized trade.

They face their own threat from the party's right wing, where anti-immigration elements have allied with antitrade Democrats on the job-loss issue.

"It's not trade that they're worried about as much as it is immigration and having a single market," said Weintraub.