"I don't support, I don't believe the administration supports a wall," Commissioner W. Ralph Basham said in Tucson, where he met with patrol officials and agents before embarking on a tour across the Arizona desert.

Asked about proposals in Senate- and House-approved immigration measures to build security walls 380 or 700 miles long, respectively, Basham said, "It doesn't make sense, it's not practical."

As Arizona Gov. Janet Napolitano put it, "You build a 50-foot wall, somebody will find a 51-foot ladder," he said.

Fencing, including so-called smart fencing with imbedded sensors, vehicle barriers and lighting will be part of the infrastructure improvements needed, Basham said. But a layered approach that mixes technology and air operations for observation and responding to illegal crossings will be necessary to control the border, he said.

"There is not a silver bullet out there, there's not one answer," he said.

Basham is touring the Southwest border region for a firsthand look at the challenges the Border Patrol is facing as National Guard troops arrive to begin assisting efforts to control the border.

"You can sit in Washington, D.C., and you can get briefings and you can look at maps and hear from people what the challenges are out here," Basham said. "But until you get up there and you look and you see what kind of terrain you're dealing with and the difficulties of it, you really don't have a true appreciation."