Enlarge By Matt York, AP A fence runs along the border between Nogales, Ariz., and Mexico. President Obama will send 1,200 National Guard troops to help secure the U.S.-Mexico border, an administration official and an Arizona congresswoman said Tuesday. PUBLIC OPINION PUBLIC OPINION From Truman to Obama, see each president's ratings with USA TODAY's approval tracker.

A month after Arizona passed an immigration law that reignited a national debate, President Obama is sending up to 1,200 National Guard troops to help secure the U.S.-Mexico border.

The troops will be a "bridge to longer-term enhancements" on the Southwestern border, helping with intelligence and surveillance while additional Border Patrol agents are trained, Obama's national security adviser, James Jones, said in a letter to Senate Armed Services Chairman Carl Levin, D-Mich.

Obama will also request $500 million for border protection and law enforcement, Rep. Gabrielle Giffords, D-Ariz., said.

ACROSS THE BORDER: Activists blast Mexico's immigration law

The decision came to light after Obama met with Senate Republicans to discuss immigration legislation — a package that could be difficult to pass this year without Republican support, White House spokesman Bill Burton said.

Asa Hutchinson, the first Homeland Security undersecretary for border security under President Bush, said, "The numbers that they're going to add will help, but it's not going to fix the problem."

Frank Sharry of America's Voice, a group that supports tighter borders as well as a way for illegal immigrants to earn citizenship, said Obama seemingly gave in to Republican leaders without assurance on more comprehensive immigration legislation.

"Talk about one step forward and two steps back," Sharry said.

Roy Beck of NumbersUSA, a group that wants to reduce legal and illegal immigration, was pleased but called the action a minimal response and based on politics.

"I think the White House people are watching the polls and seeing how incredibly popular the Arizona law is," Beck said. The law requires police to check immigration status if they suspect that someone they detain is in the country illegally.

Janet Murguia, president of the National Council of La Raza, a Hispanic civil rights organization, said the decision to focus first on border security rather than fix immigration law was "deeply disappointing."

Arizona's Republican senators, John McCain and Jon Kyl, pointed to the 6,000 troops President Bush sent in 2006 as an example of the manpower needed. Arizona's Democratic attorney general, Terry Goddard, called Obama's move a "good start."

Pinal County Sheriff Paul Babeu, whose jurisdiction includes the busy human- and drug-trafficking corridor between Tucson and Phoenix, said he appreciates the troops. "But it's not enough."

Contributing: Kevin Johnson in Washington, The Arizona Republic.