The U.S government waived environmental and other regulations that it said on Tuesday threatened to delay completion of nearly 500 miles of a planned barrier fence along the border with Mexico.Homeland Security Secretary Michael Chertoff, who has chafed at obstacles to the controversial barrier project, issued the waivers for stretches of land in California, Arizona, New Mexico and Texas. The fence is intended to deter illegal crossings by immigrants, drug runners and others. "Criminal activity at the border does not stop for endless debate or protracted litigation," Chertoff said in a statement. "Congress and the American public have been adamant that they want and expect border security. We're serious about delivering it."