ASSOCIATED PRESS WRITER

ISAAC LEVI

MEXICO CITY (AP)—The chief of General Motors threw the giant automaker’s full weight behind the North American Free Trade Agreement Thursday. He denied that NAFTA would drain off U.S. jobs and called arguments against it ‘‘ludicrous.’‘

John F. Smith Jr., GM’s chief executive officer and president, said that as a major employer, manufacturer, and marketer in Canada, Mexico and the United States, ‘‘we have been a strong supporter of NAFTA from the outset.’‘

‘‘NAFTA will create new jobs in all three countries as trade among them increases.

‘‘And that’s why I find much of the rhetoric being espoused in the NAFTA debate in my own country to be especially alarming and ludicrous,’‘ Smith said.

‘‘Opponents to NAFTA in the U.S. keep making dramatic and emotional charges that it will somehow drain jobs from the U.S. to Mexico. I think they’re just dead wrong.’‘

Smith, on his first visit to Mexico, addressed a luncheon gathering in his honor by the American Chamber of Commerce.

The treaty has been ratified by the Canadian Parliament and is a shoo-in for approval by the Mexican legislature. But foes in the U.S. Congress want to scuttle it because of fears it will siphon jobs to Mexico, where wages are low and environmental enforcement is often poor.

NAFTA aims to create the world’s biggest trading bloc, with 360 million consumers and $6.4 trillion a year in total trade, including services.

President Carlos Salinas de Gortari says free trade will be dead for many generations if NAFTA is not in place as scheduled by Jan. 1. He rejects all suggestions of renegotiating it.

Salinas cautions that even without NAFTA, Mexico will go ahead with trade liberalization and seek other block-trade partners in Western Europe, the Pacific Rim and the rest of Latin America.

A dozen Latin American chiefs of state backed Mexico at a meeting in Chile this week, which Salinas attended.

Smith cited U.S. Commerce Department estimates of increases in Big Three vehicle exports to Mexico of $1 billion during the first year alone of NAFTA, ‘‘which translates into 15,000 jobs in the U.S. auto and supplier industries.’‘

The GM boss said his ‘‘own feeling is that the trend of trade liberalization is irreversible regardless of what happens with NAFTA.’‘