Military surveillance planes will begin patrolling the southwest border in January

The Homeland Security Department will start positioning military aerial surveillance aircraft in the southwest United States in January 2012 as part of a new border security strategy, federal officials announced Tuesday.

Defense Department drones will not be part of the fleet, an official said.

The move marks the expansion of a Defense-Homeland Security partnership that previously centered on National Guard ground patrols assisting civilian law enforcement authorities. Now sophisticated Pentagon technology will be added to the mix.

"The addition of aerial surveillance assets allows the National Guard to better support DHS by shifting surveillance from fixed sites to mobile ones that can quickly match the dynamic environment of the border -- a significant enhancement in the ability to detect and deter illegal activity at the border -- and provide greater support to the thousands of men and women involved in border security," Homeland Security officials said in a statement.

Under the arrangement, fewer National Guard personnel will be stationed at the border. "The deployment of these new DoD technical assets, along with the additional DHS personnel on the ground, will enable DoD to reduce the number of National Guard troops at the southwest border while enhancing border security," Homeland Security officials said.

The additional planes should be in place by March 1, according to officials. The "rotary and fixed-wing" vehicles are expected to overcome the problem of seeing illegal activity in rugged terrain, a challenge that derailed a $1 billion virtual fence project.

The military aircraft also are intended to deter undocumented foreigners from trying to cross the border, DHS officials said. And the Defense vehicles can more quickly ferry Border Patrol agents from one location to another when illicit activity such as drug smuggling is spotted.

Earlier this month, Homeland Security officials put out a preliminary call to contractors for military- or industrial-grade surveillance towers to replace the now-defunct Secure Border Initiative network fence. Officials plan to issue a final solicitation for bids in January or February.

Defense, State Department and Federal Aviation Administration officials have raised concerns about flying Pentagon drones -- remotely piloted surveillance aircraft -- in the Southwest. In September, federal auditors reported that State and Pentagon officials were afraid of creating the appearance of a militarized border at a time when the U.S. government is helping Mexican civilian authorities combat drug cartels. Also, unmanned aircraft can endanger piloted commercial planes, according to FAA.