The 9th U.S. Circuit Court of Appeals denied a request made by the Teamsters union, the Sierra Club and the nonprofit Public Citizen to halt the program.
The appeals court ruled the groups have not satisfied the legal requirements to immediately stop what the government is calling a "demonstration project," but can continue to argue their case.
The trucking program is scheduled to begin Thursday.
In court papers filed this week, the Teamsters and Sierra Club argued there won't be enough oversight of the drivers coming into the U.S. from Mexico.
They also argued that public safety would be endangered in a hasty attempt by the government to comply with parts of the North American Free Trade Agreement.
The trade agreement requires that all roads in the United States, Mexico and Canada to be opened to carriers from all three countries.
Canadian trucking companies have full access to U.S. roads, but Mexican trucks can travel only about 20 miles inside the country at certain border crossings, such as ones in San Diego and El Paso, Texas.
The government contends that further delays in the project will strain the relationship between the U.S. and Mexico.
In court filings this week, government lawyers said that the program is an important interim step in fulfilling the United States' obligations under NAFTA. They said that Mexican trucking companies would have to meet the same regulations governing U.S. trucking companies, and that in some cases the requirements are stricter.
Representatives of the Teamsters did not immediately return calls late Friday from The Associated Press, and a Sierra Club spokeswoman declined to comment immediately.
