Trump says 23-year-old trade deal with Canada, Mexico 'worst' in history.

Representatives from the U.S., Canada and Mexico met Wednesday in the nation’s capital to revise a deal that Washington insists is necessary for fair trade.

The 23-year-old North American Free Trade Agreement (NAFTA) has cost the U.S. hundreds of thousands of jobs, Trade Representative Robert Lighthizer said during the opening round of talks.

"We feel that NAFTA has fundamentally failed many, many Americans and needs major improvement," he said, praising President Donald Trump for pushing renegotiations.

Trump, who made job growth the centerpiece of his campaign for the Oval Office last year, characterized NAFTA as the "worst deal ever made in the history of the world" and vowed to fix it.

Representatives from Mexico and Canada struck a different tone Wednesday, setting the stage for a contentious climate during the four-day talks.

Canadian Foreign Minister Chrystia Freeland said NAFTA's record was "one of economic growth and job creation.

"We are steadfastly committed to free trade in the North American region and to ensuring that the benefits of trade are enjoyed by all Canadians," she said.

Mexican Secretary of Economy Ildefonso Guajardo conveyed similar sentiments about the pact he called a "strong success for all parties."

NAFTA did away with tariffs on most goods and introduced new labor standards and intellectual property rules when it took effect in 1994.

The renegotiation process began in earnest in May after the Trump administration told Congress it would seek changes to the current deal "to support higher-paying jobs in the United States and to grow the U.S. economy."

While supporters and critics have traditionally felt strongly about the pact, a nonpartisan report published that same month by the Congressional Research Service suggested the trade deal’s effect has been "relatively modest.

"The political debate surrounding the agreement was divisive with proponents arguing that the agreement would help generate thousands of jobs and reduce income disparity in the region, while opponents warned that the agreement would cause huge job losses in the United States as companies moved production to Mexico to lower costs," it said.

"In reality, NAFTA did not cause the huge job losses feared by the critics or the large economic gains predicted by supporters. The net overall effect of NAFTA on the U.S. economy appears to have been relatively modest, primarily because trade with Canada and Mexico accounts for a small percentage of U.S. GDP.”

There is no formal deadline for the renegotiation process, but Lighthizer called the talks "the first of several rounds."

NAFTA talks begin amid US demands for major overhaul