President Barack Obama's administration said Thursday that 1,200 National Guard troops will remain on watch for drug traffickers and illegal immigrants in Arizona and other states neighboring Mexico for an additional 90 days, which analysts say is part of a political effort to demonstrate he is committed to keeping border security a priority as the 2012 election season heats up.

This is the second time the Obama administration has extended the National Guard's temporary deployment, which originally was scheduled to end in June.

The extension, which will be funded by the Department of Defense, comes as the Pentagon is facing billions of dollars in budget cuts and the Obama administration is under tremendous pressure to cut spending to reduce the deficit.

It also comes at a time when apprehensions of illegal immigrants in Arizona by the Border Patrol have plummeted and violent crime along the border is down or flat - both signs of a decline in crossings by illegal immigrants, officials say.

As Obama gears up for his re-election battle, possibly against a Republican border hard-liner, and congressional inquiries into the controversial gun-trafficking probe known as Operation Fast and Furious are gaining steam, it is unlikely that Obama would relax security measures, one political expert said.

"Immigration actually hasn't been a very strong issue in the campaign so far, but there are things on the horizon that could suggest that it could flare up again at any moment," said Kareem Crayton, a political scientist and associate professor of law at the University of North Carolina-Chapel Hill.

"The Fast and Furious investigation seems to be inching toward findings that may implicate higher-up members of the government. There are going to be questions raised as to who in the Washington establishment knew about it or directed it."

Operation Fast and Furious was a botched investigation that resulted in the Bureau of Alcohol, Tobacco, Firearms and Explosives losing track of an estimated 1,800 guns, many of which crossed the border into Mexico and some of which have been connected to crimes.

Two Fast and Furious guns were found at the scene of a southern Arizona shootout that left Border Patrol Agent Brian Terry dead. Dennis Burke, the U.S. attorney for Arizona, resigned Aug. 30 as a result of the scandal.

Obama also most likely doesn't want to take a chance that something might go wrong on the border after the National Guard withdraws, which would be a political liability.

It's possible that a decision such as keeping the Guard in place could be "considered decent policy while also definitely politically protective," Crayton said. "They probably are exercising an abundance of caution."

The troops have been stationed along the border since summer 2010 to help stem the flow of drugs and illegal immigrants into the United States. They primarily provide support to the Border Patrol and other law-enforcement agencies.

Obama authorized 1,200 National Guard troops, though the number fluctuates as troops rotate in and out of the job. Currently, there are about 1,120 troops stationed along the border, including 492 in Arizona, 277 in Texas, 266 in California, 68 in New Mexico and some at a separate command center, said Rod Korba, a spokesman for the National Guard Bureau in Arlington, Va.

The temporary deployment was scheduled to end June 30 but was extended until Sept. 30, the end of the federal government's fiscal year. The troops will now remain until the end of December, said Lt. Col. Robert Ditchey, a spokesman at the Office of the Secretary of Defense.

He said Defense Secretary Leon Panetta announced the extension on Thursday at the request of the Department of Homeland Security.

Ditchey did not say how much it will cost to keep the troops on the border for an additional three months, but the most recent extension cost $35 million.

U.S. Sen. John McCain, R-Ariz., said he appreciated the administration's move, although he would like to see the Guard's mission extended.

"It makes one curious about their continued statements about the border being secured," said McCain, the Senate Armed Services Committee's ranking GOP member. "If the border is secured, then obviously those additional troops wouldn't be necessary."

McCain said he's not worried about the cost of the longer Guard mission. He said defense savings can come from reining in cost overruns on weapons systems and elsewhere.

"I think it's certainly affordable," McCain said. "It's high on my priority list."

Arizona Gov. Jan Brewer said she was "gratified" by the move and "appreciative" but questioned the long-term viability of the proposal.

"The fact of the matter is that it is probably not enough time," Brewer said. "We want our border secured."

Matthew Chandler, a Homeland Security spokesman, said the troops will stay on the border while more agents are trained and more technology and infrastructure is added to beef up border security.

"The Department of Homeland Security is actively training new personnel and implementing new technology to enhance our border-security architecture," he said.

There now are more than 20,700 Border Patrol agents, according to the DHS. The agency is continuing to add agents as part of an emergency $600 million spending bill passed last summer by Congress that provided for 1,000 Border Patrol agents, 250 Customs and Border Protection officers and two unmanned aircraft that provide surveillance along the border.

Through July 31, the Border Patrol's Tucson Sector, the nation's busiest, has logged 109,000 apprehensions of illegal immigrants, down 44 percent from the same period the previous year, said Colleen Agle, a Border Patrol spokeswoman. Agents in the Tucson Sector have seized 876,000 pounds of marijuana through the end of July, up 1 percent from the same period the previous year, she said.

Capt. Valentine Castillo, a spokesman for the Arizona National Guard, said the troops deployed along the border serve as "eyes and ears" for the Border Patrol and other federal law-enforcement agencies.

They are positioned in strategic observation posts along the border and alert the Border Patrol when they see suspicious activity, he said. The troops do not carry out any law-enforcement duties and are armed only for self-defense purposes, he said.

Rick Van Schoik, director of the North American Center for Transborder Studies at Arizona State University, said deploying Guard troops along the border makes sense because it helps free up more Border Patrol agents to look for drug traffickers and human smugglers. The troops also act as a deterrent, he said.

But it is difficult to measure whether the millions of dollars that have been spent to deploy the troops have been cost-effective, he said.

Republic reporter Ginger Rough contributed to this article.