The Bush administration said Wednesday it will fortify the westernmost stretch of the U.S.-Mexico border over the objections of environmentalists and California regulators, who feared the project would harm a refuge for endangered birds. Homeland Security Secretary Michael Chertoff signed an environmental waiver Tuesday night that expedites the Border Patrol's long-standing plans to fill in canyons and erect additional fencing along the final 3 1/2 miles of the border before it meets the Pacific Ocean...

Chertoff said the fortifications would help reduce illegal border crossings, while Border Patrol Chief David Aguilar told reporters the project was "not directly related to illegal immigration," but a broader effort to close gaps that terrorists and others could exploit. "This is about border security," Aguilar said...

Aguilar said the Border Patrol may move to fortify the border in other areas, although both he and Chertoff said the administration had no plans to wall off the entire 2,000-mile Southwest border with Mexico.

Concern over illegal immigration led Congress to pass legislation in 1996 requiring the Border Patrol to strengthen the westernmost 14-mile stretch of the border. Nine miles were fortified, but environmental concerns and lawsuits held up construction on the last 3.5 miles leading to the ocean and 1.5 miles farther east. Earlier this year, Congress gave Chertoff the power to sign a broad environmental waiver to finish the job, citing fears that terrorists could slip through an unsecured border...