The United States drew a hard line for renegotiating the North American Free Trade Agreement on Wednesday, demanding major concessions aimed at slashing trade deficits with Mexico and Canada and boosting U.S. content for autos.

At the start of talks in Washington, U.S. President Donald Trump's top trade adviser, Robert Lighthizer, said Trump was not interested in "a mere tweaking" of the 23-year-old pact, which Trump has threatened to scrap without major changes.

"We feel that NAFTA has fundamentally failed many, many Americans and needs major improvement," Lighthizer, the U.S. trade representative, said at the start of the talks, which reflected Trump's relentless criticism that NAFTA has caused massive job losses in the U.S. manufacturing industry.