Mexico-U.S. border trucking full of potholes

"Anything that will lubricate the wheels of global trade is good news," Woolson said.

The U.S. Federal Motor Carrier Safety Administration, in charge of the project, says Mexican truck companies will be held to more stringent standards than their U.S. counterparts and that to meet NAFTA obligations the test must go ahead.

FMCSA spokeswoman Melissa DeLaney said the goal is to ease trade and increase competition for cross-border transport. A similar arrangement has existed on the U.S.-Canadian border for decades, she said.

Jackie Gillan, vice president of Advocates for Highway and Auto Safety, said that comparison was misleading.

"The regulatory environment of the United States is much, much closer to that of Canada than it is to the environment in Mexico," she said. "It's not an apples to apples comparison, it's apples to oranges."

Union opposition focuses on safety. But labor groups also fear that opening up the border will lead to lower-paid Mexican drivers taking over U.S. trucking jobs and add to outsourcing of U.S. manufacturing jobs to non-unionized Mexican firms.

"Job security is an issue for us," said Leslie Miller, a spokeswoman for the International Brotherhood of Teamsters.

DeFazio said that opening the border will lead to dangerous Mexican trucks and truckers - many of whom he claims take stimulant drugs to stay awake for days on end to drive - and pose a "safety risk to U.S. families and school buses."

"While Mexico is a country where corruption is rife and there is no respect for the rule of law or regulation, we will not consider backing this project," DeFazio said.

Arizona Trucking Association's Woolson disagreed. "All we get is a stereotype of an unsafe, drugged-out Mexican trucker," he said. "This isn't debate, it's ludicrous hysteria."