Department of Transportation officials are urging more Mexican companies to apply for the cross-border pilot program that went into effect last fall.

So far, 21 Mexican companies have applied to the program; two have received final clearance. Transportes Olympic of Monterrey began making crossings in October. Moises Alvarez Perez of Tijuana has not get crossed with a shipment.

Operating authority for a third carrier, Grupo Behr de Baja California, is on hold pending additional review.

According to a report in U-T San Diego, DOT officials met with Mexican truckers Friday at a hotel in Tijuana to discuss the program. Without enough trucks in the program, they said, the agency won't be able to determine that Mexican trucks can operate safely in the U.S. under the North American Free Trade Agreement.

Members of Mexican trucking group Canacar who attended Friday's session complained that Mexican truckers face more stringent requirements than their U.S. counterparts under the current pilot project, according to the paper.

The three-year pilot program sets up a vetting and enforcement program to ensure the safety of Mexican trucks, with the goal of evaluating their safety performance, based on inspections at the roadside, ports of entry and weigh stations, and on traffic enforcement.

It's the newest version of a story that has been going on since the United States and Mexico signed the North American Free Trade Agreement in 1994. In past versions the administration in office, Democrat or Republican, diligently looked for ways to implement the cross-border trucking provision of NAFTA while the Teamsters union, OOIDA, safety advocacy groups and environmental groups just as diligently looked for ways to scuttle the plan.

After Mexico upped the ante with retaliatory tariffs on U.S. products, the FMCSA announced last July it was implementing the new pilot program.