Guard has been "very useful." Ed Andrieski

PHOENIX - The Obama administration is having second thoughts about withdrawing all National Guard troops from the border by the end of June.

The National Guard Bureau in Virginia is asking Arizona officials for input on "different courses of action" for what to do about the 560 soldiers now assigned to border-security duty in Arizona, part of 1,200 troops placed along the entire Mexican border. Lt. Valentine Castillo of the Arizona National Guard said Tuesday that one of those options is to extend the mission.

And Homeland Security Secretary Janet Napolitano, in an interview with Reuters, said the administration is weighing whether to keep troops there to tamp down border violence.

"They have proven to be very, very useful at the border," the former Arizona governor said. "They have helped in a number of drug seizures, among other things."

But Napolitano said there has been no "final decision about whether and at what strength to leave the Guard at the border."

A decision is needed soon.

Federal funding runs out in June. But Castillo said it is necessary to start the "ramp-down" process by the middle of next month to ensure that everything is wrapped up by that date.

Sensing a possible opportunity, Gov. Jan Brewer on Tuesday sent a letter to the president outlining some accomplishments of Arizona Guard troops, including assisting in apprehensions of border crossers and helping to seize 18 tons of marijuana.

"I am concerned that when the current mission ends in June, the gains we have made will be immediately lost," Brewer wrote. "Arizona can ill afford that kind of loss in the effort to secure the border."

The White House would not comment, referring all inquiries to Napolitano's agency.

Matt Chandler, Napolitano's press aide, had no specific comment about the continued need for troops.

But he said Border Patrol staffing now is better than it ever has been. There are currently about 20,700 agents - including 3,700 in the Tucson Sector alone - compared with 10,000 just seven years ago.

And Chandler said the situation has changed since last year when the troops were first authorized. That includes funding for another 1,000 Border Patrol officers, with 859 for the Tucson sector.

That legislation also authorized 250 new Customs and Border Protection officers at ports of entry, 250 new investigators for Immigration and Customs Enforcement and two new forward operating bases "to improve coordination of border security activities."

Brewer, in Tuesday's letter to Obama, also asked for "a serious commitment to a substantial border fence, one that is difficult to overcome and well maintained."

Homeland Security officials say the agency has completed 649 miles of fencing along the U.S.-Mexico border, including 299 miles of vehicle barriers and 350 miles of pedestrian fence.

And the governor repeated a call she made two years ago to put another 250 soldiers along the border as part of a separate, ongoing Joint Counter Narco-Terrorism Task Force. There are currently 150 soldiers in that program.