NOGALES, Ariz. -- On her first trip back to Arizona as Homeland Security secretary, Janet Napolitano said Wednesday that requests for putting the National Guard back along the Mexican border are under review.

Arizona's former governor said President Obama wants to know what missions the soldiers would perform.

At a news conference announcing a $212 million renovation of the Mariposa commercial port of entry inspection facility at Nogales and added resources -- and money -- for federal, state and local law enforcement in efforts to prevent a spillover of drug-cartel violence, Napolitano was asked about restoring the Guard's presence on the border with Mexico.

Napolitano said the president is looking at the requests from Govs. Rick Perry of Texas and Jan Brewer of Arizona.

Thousands of Guard troops performed various support duties along the border for two years during the Bush administration, from building fences to reporting illegal immigrants, to free Border Patrol agents to focus on border security.

Meanwhile, at a Phoenix-area luncheon sponsored by the Arizona Chamber of Commerce and Industry on Wednesday, U.S. Sens. John McCain and Jon Kyl called for returning troops to the border to assist against violence spilling over from the drug war in Mexico.

McCain said the government should respond to Perry's and Brewer's requests because of the drug violence in Mexico. Kyl said the Guard was effective in assisting the Border Patrol and in deterring immigrant and drug smuggling operations. The Arizona Republicans said the need for the troops now is real.

"I don't envision it for an extended period of time, but right now, we need the Guard on the border because of this violence," McCain said in response to a question from an Arizona National Guard member.

Mexico's government is battling drug cartels at the same time that drug groups are fighting each other for the most lucrative smuggling routes into the United States. More than 10,650 people have been killed in drug violence in Mexico since President Felipe Calderon sent out 45,000 troops in 2006 to directly confront the traffickers.

The Bush administration also sent thousands of National Guard troops to the border to perform support duties in a mission called "Operation Jump Start" that began in 2006 and ended last year. It was intended to free up U.S. Border Patrol agents to focus on border security while new agents were hired. But since the troops pulled out, violence among Mexican cartels has exploded.

Napolitano said the president is considering the requests from the border governors with an eye to how the Guard might be used.

"The president ... really has asked questions particularly of the governor of Texas, who was the first one to request it, saying, `Where would they go, what missions would they perform?,"' Napolitano said. "In other words, don't just throw something like the National Guard at a place. They have a mission and a job to do.

"When we did Jump Start here, it was to help us build the fence along this portion of the border. So that's being looked at right now," added Napolitano. "The National Guard issue, without being state-specific, is under consideration."