NEW ORLEANS, April 22 (Xinhua) -- The leaders of the United States, Canada and Mexico concluded their two-day summit here Tuesday, giving a symbolic boost to the 14-year-old North American Free Trade Agreement (NAFTA).

    The annual gathering, like its previous versions since 2005, provided an opportunity for the North American leaders to strengthen ties and take stock of achievements made in mutual cooperation.

    The leaders spent the two days discussing a broad spectrum of issues, including trade, food safety, emergency response, energy supply, border security, environmental protection and organized crime.

    But other than reaffirming a unified stand toward free trade, the "Three Amigos Summit" produced few substantial outcomes, as analysts had predicted, partly because U.S. President George W. Bush is set to step down early next year.

    Along with his Mexican counterpart Felipe Calderon and Canadian Prime Minister Stephen Harper, Bush used almost every occasion at the summit to stress the importance of and rally support for NAFTA, which has linked the three economies since 1994.

    All three leaders emphasized the benefits of the agreement, saying it has helped create jobs, improve services and enhance people's quality of life.

    According to U.S. government figures, trade among the NAFTA nations more than tripled between 1993 and 2007, going from 297 billion U.S. dollars to 930 billion dollars.

    "Now is not the time to renegotiate NAFTA or walk away from NAFTA," Bush told a joint press conference capping the summit. "Now is the time to make it work better for all our people. And now is the time to reduce trade barriers worldwide."

    Bush criticized senators Hillary Clinton and Barack Obama, both candidates for the Democratic party's presidential nomination, for their calls to renegotiate NAFTA or even pull back from it.

    He also blamed Nancy Pelosi, the Democrat House speaker, for holding up a vote on a free trade agreement with Colombia.

    His comments were echoed by both Calderon and Harper, who also gave examples of NAFTA's benefits.

    "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."

    Harper said NAFTA was "critically important" for jobs and prosperity on both sides of the border, asserting that to renegotiate it would be a mistake.

    Both Calderon and Harper threw their weight behind Bush in his push for a free trade agreement with Colombia, saying that such a deal would benefit everyone.

    Canada is also currently trying to negotiate a free trade agreement with Colombia while Mexico already has one with the South American country.