WASHINGTON, D.C. --- Citing safety concerns, U.S. senators from both parties have attached a measure to a transportation spending bill to block funding for the Bush administration's cross-border trucking program. The Senate vote was 74-24. The House approved a similar measure earlier this year. According to the Los Angeles Times, the White House issued a statement this week saying it "strongly opposes" efforts to delay the one-year pilot truck program, which permits Mexican trucks to travel throughout the U.S. Previously, Mexican trucks were restricted to a narrow zone north of the U.S.-Mexican border where they transferred cargo to American big rigs. Opponents of the pilot program argue that Mexican truck operators adhere to weaker safety standards, posing a risk to the American public. Backers of the program, however, say that critics are protectionists afraid of free trade. The Bush administration has said that Mexican trucks will be subject to rigorous safety inspections, and drivers will be subject to drug testing. Opponents of the program include the Teamsters and the Sierra Club.