In a speech on immigration policy Monday evening, President Bush is expected to announce an expansion in the use of National Guard troops along the U.S.-Mexico border to help reduce the flow of illegal immigrants. But at the Defense Department, officials say that does not mean border control is being transferred to the military.

Illegal immigrants detained by US Border Patrol

The long U.S. land borders with both Mexico and Canada are not patrolled by the military. Rather, border enforcement is the job of the Border Patrol, a civilian police agency under the Department of Homeland Security.

But the Border Patrol on the Mexico-U.S. border has been unable to stop the flow of illegal immigrants from throughout Latin America, who are desperate for jobs and other benefits of living in the United States. They come hidden in vehicles across established checkpoints, and also by foot, through remote areas where patrols are difficult and fences are minimal.

So, as part of his broad immigration policy, which also includes plans to address the status of the estimated 12 million illegal immigrants already in the country and a plan for a Guest Worker Program, President Bush is expected to announce that he is sending the National Guard to help the Border Patrol.

US National Guard HMMWV

But Defense Department officials are eager to make clear that this does not mean the border will be militarized. They say no National Guard troops will be on the front lines, involved in apprehending or detaining illegal immigrants. Rather, spokesman Bryan Whitman says, the National Guard will provide such services as communications, logistics, intelligence analysis and surveillance, including the use of high technology unmanned aircraft.

"This will be support to the Department of Homeland Security," said Bryan Whitman. "It'll be much of the same type of pre-existing missions that the Guard already does."

Bryan Whitman

Whitman says about 300 National Guardsmen are already providing such support for the Border Patrol along some sections of the U.S.-Mexico Border.

Another official, who spoke on condition of anonymity, said specifically that no soldiers will be "pointing guns" along the border. The official said, fewer than 10,000 Guard members will be deployed in the support roles, in part to free members of the Border Patrol to take the front line positions. The official said the policy is intended to be temporary, until the Border Patrol can recruit and train additional officers, and take on all the functions by itself, but he would not say how long the program is expected to continue.

The National Guard is a reserve force organized in each state. It has responsibilities to the state governors, and officials say they are working on the legal structure needed for interior states to lend Guard members to border states for this project. The Guard also falls under the national military command structure. Members can be called to active military duty as needed, and they have played crucial roles in the Iraq and Afghanistan wars. Officials say this expanded border assignment for the National Guard will not affect the rotation of units to those conflicts.