Updated

The Obama administration is considering a one-year plan to send up to 1,500 National Guard volunteers to the southern border to help build an existing counter-drug effort along the Mexican border.

A senior White House official told FOX News on Tuesday that President Obama is concerned about the situation at the border and wants to work with Defense Secretary Robert Gates and Homeland Security Secretary Janet Napolitano on the question of additional resources, including a beefed up National Guard presence.

The Pentagon has expressed concerns about committing more troops to the border -- a move some officials worry will be seen as militarizing the region. Since the issue is still being debated, no decisions have been made yet, said the official, who spoke on condition of anonymity because of the ongoing internal policy debate.

According to senior administration officials who spoke to The Associated Press, the federally funded program, which could cost as much as $250 million, would call on National Guard volunteers from the four border states who would perform surveillance, intelligence analysis and aviation support. Arizona, California, New Mexico and Texas have more than 50,000 Army and Air National Guard members.

Guard units would also supply ground troops who could assist at border crossings and with land and air transportation, but they would not be involved in law enforcement.

Earlier this spring Obama promised Mexican President Felipe Calderon that the United States would help with the escalating drug war, which has killed as many as 11,000 people since December 2006.

Attorney General Eric Holder and Napolitano announced a 2009 counternarcotics strategy several weeks ago, saying the U.S. would devote more resources to fighting the Mexican drug cartels, including the cash and weapons that flow across the border from the U.S. into Mexico.

But officials say Gates has expressed concern that tapping the military for border control posts is a slippery slope and must not be overused.

Paul Stockton, assistant secretary of defense for homeland defense, said Monday that options for the new program have been drafted, but the plan still must be reviewed and acted on by key Cabinet members as well as the president.

"We have been working very closely to build a set of options that would have the Department of Defense in a very limited way, for a limited period of time, serve in direct support for CBP," said Stockton, referring to Customs and Border Protection.

The administration does not want to announce or begin the effort until after the Mexican elections this week, officials said.

Rand Beers, undersecretary for national protection at the Homeland Security Department, declined to say how long the program would last, only that it would not be lengthy. Beers said the additional Guard members would stay as long as needed for the border patrol agents to be trained and given "some period of time" on the border to gain experience on the job.

Officials came to the decision that it is simply not enough for the United States to provide funding in support of the Mexican government's counter-drug efforts, said Beers.

The current National Guard counter-drug operation along the border, which has been in effect for many years, involves about 575 Guard members, who applied for the job through their state program coordinator.

A previous program -- Operation Jump Start -- used National Guard troops to help bolster border patrols for three years. Over that time, the federal government added border patrol agents, but the escalating drug war has stretched those forces as they try to increase surveillance of possible cash and arms traffic.

FOX News' Mike Emanuel and The Associated Press contributed to this report.