Updated

The Defense Department announced Tuesday that the Obama administration plans to keep a reduced contingent of National Guard troops working along the Mexican border for the next year.

Starting in January, the force of 1,200 National Guard troops at the border will be reduced to fewer than 300 at a cost of about $60 million, said Paul Stockton, assistant secretary of defense for homeland defense.

The remaining troops will shift their focus from patrolling the border on the ground looking for undocumented immigrants and smugglers to aerial surveillance missions using military helicopters and airplanes equipped with high-tech radar and other gear. Exactly where those troops will fly or how many aircraft will be used has not been decided, he said.

"We are basically going from boots on the ground to boots in the air," said David Aguilar, deputy commissioner for Customs and Border Protection.

Border Patrol Chief Michael Fisher said his agency is working on identifying the "areas of greatest concern" along the border — areas that include Arizona and South Texas — and will station troops and aircraft accordingly.

President Barack Obama ordered a second round of Guard troops to the border last year, with the first of those troops arriving in California, Arizona, New Mexico and Texas in August 2010. President George W. Bush first ordered Guard troops to the southern from 2006 to 2008. They were supposed to be in place for about a year but Obama extended the deployment earlier this year. The smaller force is now expected to remain until the end of 2012.

Stockton said the remaining troops are "transitioning to much more effective support."

"This provides us with more flexibility in dealing with the persistent challenges posed by cross-border movement and illegal crossings," Stockton said.

According to the Government Accountability Office, the Pentagon has previously spent about $1.35 billion for the deployments under Bush and Obama.

Stockton said the Pentagon has budgeted about $60 million for the mission in 2012.

Congressional Republicans have objected to reducing the number of troops, arguing that the border isn't secure and reducing the number of people patrolling the area doesn't help security.

"If the Obama administration's goal is border security, their actions undermine their objective," said Rep. Lamar Smith, a Texas Republican and chairman of the House Judiciary Committee. "The administration's decision to draw down the National Guard troops along the U.S-Mexico border makes an already porous border worse."

Aguilar, who previously led the Border Patrol, said Tuesday there is still work to be done at the border but that successes in securing the frontier have allowed DHS to reduce the number of troops and change the mission.

In the fiscal year that ended Sept. 30 Border Patrol agents at the southern border made 327,577 arrests, the fewest since 1972. There are also more than 18,500 agents patrolling the border, the highest number in the agency's history.

When Bush first deployed the National Guard, there were just over 11,000 Border Patrol agents in the area who made more than one million arrests.

Based on reporting by the Associated Press. 

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