SAN ANTONIO (Reuters) - The first Mexican truck bound for the U.S. interior crossed at the international bridge at Laredo, Texas, on Friday, carrying electronic equipment destined for suburban Dallas and fulfilling a controversial provision of the 1994 North American Free Trade Act.

The move was praised by business leaders on both sides of the Rio Grande, while sign-waving Teamsters Union members in Laredo jeered.

NAFTA called for Mexican trucks to be allowed to travel beyond a six- to 25-mile wide "commercial zone" in the United States by December of 1995.

However, concerns about the safety of Mexican trucks, the opposition of the Teamsters and other labor unions, and, in the past several years, heightened concerns about Mexico's violent drug war and illegal immigration, have repeatedly delayed the provision from taking effect.

Canadian-based trucks have had free access to U.S. highways since 1982.

An hour before the truck left the Nuevo Laredo departure point for Garland, Texas, Mexico lifted punitive tariffs it had imposed on dozens of imports from the United States in 2009 in response to the U.S. failure to implement the cross-border trucking provision, a move the National Organization of Manufacturers said cost the loss of 25,000 U.S. jobs.

U.S. pork and dairy producers -- whose products were among those affected by the Mexican tariffs -- said Friday's action will be a major boost to their industries.

"It is a huge relief to dairy producers that their products will no longer be caught in the crossfire of a dispute not of their making," U.S. Dairy Export Council President Tom Suber told Reuters.

Doug Wolf, president of the National Pork Producers Council, said in a statement that: "Mexico is a very important market for the U.S. pork industry and for many other sectors.

"It is important that the United States abide by its NAFTA obligations and does not yield to protectionist forces."


But James Hoffa, president of the International Brotherhood of Teamsters, criticized the move.

"Mexico does not meet our safety standards and a violent drug war is raging there, which the Mexican government is powerless to control," Hoffa said in a statement.

"The Teamsters' fight to keep our roads safe will continue, and we fully expect Congress to take action, as it has in the past, to prevent Mexican trucks from being granted permanent authority to enter the United States."

A bipartisan Congressional group -- 13 Republicans and 31 Democrats -- are vowing to try to keep Mexican trucks from traveling on U.S. highways.

They say Mexican trucks are unsafe, Mexican drivers are not trained to the same standards as U.S. truckers, and opening the U.S. border to Mexican trucks will "create a security breach along out southern border," according to a letter the 44 wrote to Secretary of Transportation Ray LaHood in May.

"The current system of Mexican carriers operating within a defined commercial zone is working well for both safety and border security," the letter said.

There have also been concerns Mexican truckers will abandon their loads and become illegal immigrants.

The agreement that led to Friday's action calls for Mexican truck emissions to meet U.S. clean air standards and for Mexican trucking companies and drivers to submit to U.S. security checks.

It also says Mexican truck drivers must meet U.S. highway safety standards and demonstrate competency in English, to show they can read road signs and communicate with police.

In addition, Mexican trucks will be required to purchase U.S. insurance.

The agreement gives U.S. trucking companies equal access to Mexican highways, but few are expected to take advantage of it because transportation costs using Mexican haulers are substantially cheaper.

A 2010 study by the non-partisan Congressional Research Service questioned whether the law will have a major impact on U.S. trucking patterns, noting that during a demonstration project of the new policy in 2008, 95 percent of all trucking trips were within the border states of California and Texas, and more than 30 states had never seen a Mexican truck on their highways.

The report concluded that despite the opposition, the new trucking policy will "begin with a whimper and not a bang," and said "Mexican trucking firms will face a number of competitive disadvantages when carrying international cargo into the U.S. interior," including the need to buy U.S. insurance at what the CRS says will be the "highest possible rate."

(Editing by Jerry Norton)

Mochila insert follows.