The federal government has until early August to appeal to the Supreme Court a lower court decision that banned Mexican trucks from operating on U.S. highways beyond border commercial zones.

According to the U.S. Department of Justice, this represents a 30-day extension of time by which the government must produce a study of environmental effects of exhaust emissions from Mexican trucks.

The case involves a lawsuit by a coalition of labor, environmental and other groups that objected to President Bush's lifting a 22-year-old moratorium on Mexican trucks driving beyond U.S. commercial zones. The groups said the government should have conducted an environmental impact study before lifting the ban.