Navy Will Fix Fence on U.S.-Mexico Line : Border: The work is aimed at drug trafficking, with slowing illegal immigration as a second goal. The existing barrier has many openings.

SAN DIEGO â€”  The U.S.-Mexico border fence--sagging, full of holes and missing altogether in some spots--is due for a face lift, courtesy of U.S. Navy Seabees.

Construction units based at the Naval Amphibious Base, Coronado, will be deployed soon along the border in San Diego, authorities said. Their mission: To shore up the fence crossed daily by hundreds of undocumented immigrants heading north.

They will join California National Guard units that are improving border-area roads to assist enforcement by U.S. border guards.

Both military efforts are aimed primarily at reducing drug smuggling, but U.S. immigration authorities say the bolstered fence and improved roadways also will deter undocumented border crossers.

The existing fence poses little barrier to smugglers and immigrants. A chain-link fence stretches about seven miles east from the Pacific Ocean. Some sections have been ripped out or pounded to the ground. A raised braided cable--designed as a barrier to vehicular traffic--marks much of an additional eight miles of border, but the cable is in disrepair and there are numerous gaps.

Immigrant-rights advocates have questioned whether a so-called “Tortilla Curtain,� fixed or not, will turn back people fleeing poverty and war.

The Navy presence is the Pentagon’s latest foray into the nation’s anti-drug offensive. U.S. armed forces are increasingly providing support to civilian law enforcement, a trend that has broad support in Congress but has troubled many civil libertarians.

The Seabees, according to congressional officials, will place heavy-duty metal panels--designed for use as mats on provisional aircraft landing fields--as reinforcement along the existing barrier.

The U.S. Border Patrol, which maintains the barrier, has been using the surplus landing-pad material for more than a year in the San Diego area. Authorities say it has met with some success: No one has cut through it, although many have climbed over it and some have dug under.

“They certainly haven’t been driving through it,� said Ted Swofford, Border Patrol supervisory agent in San Diego, the busiest zone along the almost 2,000-mile U.S.-Mexico border.

So-called “drive throughs� long have been a problem in the border zone, particularly in the flat grasslands of the Otay Mesa area. A U.S. plan to dig a ditch in that area was withdrawn last year after critics likened it to a new Berlin Wall.

The Seabee unit--known officially as Amphibious Construction Battalion 1--likely will be deployed within the week, possibly by Friday, said U.S. Rep. Duncan L. Hunter (R-Coronado), who has pushed for greater use of the military in anti-drug border efforts. His district includes the entire 150-mile boundary area.

“The fence along the border is in rags,� Hunter said in a statement.

The Seabee unit and the Border Patrol will determine whether the troops will be armed, said Col. James Sutherland, a spokesman for Joint Task Force 6, the El Paso-based Pentagon arm that coordinates military involvement in anti-drug efforts along the southwest border.