Washington  - The leaders of Canada and Mexico joined with US President George W Bush on Tuesday in defending the free trade agreement between their countries, warning of the perils of a protectionist approach.

Bush met with Mexican President Felipe Calderon and Canadian Prime Minister Stephen Harper in New Orleans, Louisiana, as Democratic presidential candidates Hillary Clinton and Barack Obama continue to fault the North American Free Trade Agreement for stealing American jobs.

Bush, Calderon and Harper touted the robust economic growth that has taken place since NAFTA was enacted in 1994, saying growth has more than doubled and that hundreds of thousands of jobs have been created.

"Now is not the time to renegotiate NAFTA or walk away from NAFTA," Bush said. "Now is the time to make it work better for all of our people and now is the time to reduce trade barriers worldwide."

Senators Clinton and Obama have pledged to renegotiate the treaty as they campaign through US states hid hardest by the slumping US economy and the loss of jobs, seeking stiffer environmental and labour standards.

Calderon and Harper urged the next president, whoever it may be, to look to the future of NAFTA rather than return to the past negotiations. Calderon warned that protectionist views would be a step backwards for the US and global economy.

"This is not the time to even think about amending it or canceling it," Calderon said. "This is the time to strengthen and reinvigorate this free trade agreement among our three countries."

"My preference is not to renegotiate what we discussed in the past," Harper added.

The presumptive Republican nominee, Senator John McCain, supports NAFTA and is a strong backer of free trade.

Bush also got help from his northern and southern counterparts on his latest fight over congressional refusal to approve a free trade agreement his administration completed with Colombia.

Harper said his country was working to negotiate a similar accord with Colombia and Calderon pointed out that Mexico and Colombia were already trading freely.

"It's extremely important, I think, to bear in mind that when you provide more opportunities for trade in the Latin American region, there will be many more opportunities for prosperity," Calderon said.

Bush said a congressional failure to pass an agreement would amount to shunning a close ally in Colombia and embolden leftist leaders like Venezuelan President Hugo Chavez, who is working to diminish US influence in Latin America.

Bush said House speaker Nancy Pelosi's refusal to set a date for vote was "a bad decision on her part."

"And it's bad for our hemisphere to have the United States of America turn its back on a mutual friend like Colombia," Bush said.

The Democratic-controlled Congress believes the accord does not do enough to protect union leaders who have been violently targetted and in some cases murdered by right-wing paramiliary groups. (dpa)