To retaliate against the United States' refusal to allow Mexican trucks to do business beyond the 20-mile unloading zone on the U.S. side of the border, the Mexican government is considering stopping some U.S. trucks from doing business in Mexico.

"We don't want to take it to the point of retaliation," said Hector Marquez Solis, North American Free Trade Agreement (NAFTA) director at the Mexican Embassy in Washington. He told The Associated Press that the Mexican government is very close to taking action, but he would not say when or what kind of action the nation would take.

The U.S. unveiled a rigorous application process last year for Mexican truckers interested in driving in the country. Since then, the Dept. of Transportation (DOT) has received about 1,500 applications from Mexican truckers interested in operating north of the border.

A NAFTA provision allows truck companies in the United States, Mexico and Canada equal access to each others' roadways. But under pressure from the Teamsters union and others, the United States has barred access to Mexican carriers, citing a variety of concerns ranging from safety and security to lower wage standards.

In 2001, Mexico won a complaint before a NAFTA arbitration panel stating the United States was in violation of the trade agreement.

President George W. Bush late last year had moved to open the border to Mexican carriers, but in January a coalition of environmental and labor groups filed a lawsuit arguing the DOT had not conducted sufficient environmental impact studies before allowing the trucks into the country.

The department is set to complete that study this summer, said Ed Mortimer, senior manager of transportation infrastructure at the U.S. Chamber of Commerce.

Mexican President Vincente Fox in the past has threatened to bar U.S. trucks from entering Mexico, and for months talk of such action has permeated trucking associations along the border.