MEXICO CITY — While the internal debate continues in Washington about the validity about a cross-border trucking program with Mexico, the U.S.’s southern neighbors have taken matters into their own hands.

Last week, U.S. Congress canceled a cross-border pilot program that allowed Mexican trucks to travel freely along the U.S. highway system. In retaliation, Mexico has slapped tariffs on 90 agricultural and manufactured American exports.

Mexican Economy Minister Gerardo Ruiz said about $2.4 billion worth of exports would be affected and that his government would soon publish a list of them.

“We consider this action by the United States to be mistaken, protectionist and clearly in violation of (NAFTA)," Ruiz told reporters in Mexico City.

The U.S. had agreed to allow Mexican trucks to start using American highways by 1995 when it signed the NAFTA pact with Canada and Mexico three years earlier. But Mexican trucks were confined to border zones where they had to offload goods to be carried by domestic U.S. companies.

The cross-border program, active since 2007, allows select Mexican carriers to haul freight beyond the longstanding 25-mile commercial restriction zone at the border.

Though Congress tried to down the Bush administration’s pilot program to open the border in the 2008 appropriations, the Bush administration found a loophole in language that prohibited the "establishment" of a program, saying since the program was already established, there was no ban on continuing it.

Then, in September of last year, a Democratic-controlled Congress voted to end the program, but then-President Bush vetoed that bill and DOT officials said they would extend the program for another two years.

However, one of the conditions in President Barack Obama’s recent omnibus budget bill called for the termination of the cross-border program.

Teamsters General President Jim Hoffa, who along with a group of other protectionist agencies like Public Citizen, spent years fighting the program, arguing it made America’s roads unsafe. Hoffa applauded the House for including the ban when the budget was introduced a few weeks back.

"Shutting down the border is the right thing to do," Hoffa said. "There’s no guarantee that trucks or drivers from Mexico are safe. Until there is, dangerous Mexican trucks should not be allowed to drive freely on our highways."

Obama’s administration had said, after the omnibus budget was passed, that it would work to create a new cross-border, long-distance trucking program between the two countries.

"The president has tasked the Department of Transportation to work with the U.S. trade representative and the Department of State, along with leaders in Congress and Mexican officials to propose legislation creating a new trucking project that will meet the legitimate concerns of Congress and our NAFTA commitments," White House spokesman Robert Gibbs said.

— with files from Reuters