The administration wants to drop a court-ordered $1.8-million environmental study, which is expected to take more than a year to conduct, that has delayed the border opening.

A ruling from the 9th U.S. Circuit Court of Appeals "prevents the president's action form taking effect and thereby hampers commerce," Solicitor General Theodore Olson wrote in the government's appeal.

The ruling also needlessly prolongs a trade dispute with Mexico over the requirements of the North American Free Trade Agreement, Olson wrote.

Last November, President Bush opened U.S. highways to Mexican trucks beyond the 20-mile commercial border zones where Mexican rigs currently transfer their cargo to U.S. trucks. Under the provisions of NAFTA, Mexican trucks were to have gained full access to U.S. roads beginning in 2000.

However, a few weeks later, a coalition led by the International Brotherhood of Teamsters and the consumer group Public Citizen sued the Federal Motor Carrier Safety Administration (FMCSA) on safety and environmental grounds.

FMCSA said it could not implement safety rules governing the entry of Mexico-domiciled carriers into the U.S. until a more thorough environmental analysis had been completed, effectively blocking Mexican truck access.

FMCSA awarded a contract in August for conduction of the environmental study.