Appearing on Capitol Hill for his confirmation hearing to lead the Department of Homeland Security, retired Marine Gen. John Kelly called for a layered approach to border security and vowed that "the law will guide me" when it comes to immigration policy. 

"A physical barrier in and of itself will not do the job," Kelly, talking about a wall along the southern border, told members of the Senate Homeland Security and Governmental Affairs Committee Tuesday. "Certainly, it has to be a layered approach."

A wall would create a "balloon effect," he said, in which drug smugglers would expand operations outwards beyond the border to deliver their product. Instead, Kelly called for "layered defenses" that include patrols, sensors and drones.

Kelly, who most recently was the commanding general of U.S. Southern Command, also pushed the need to develop partnerships with Central and South American countries.

"Defense starts 1,500 miles south," he said, not just on the frontier with Mexico.

Kelly said the U.S. should help address violence in a trio of Central American countries — Honduras, El Salvador and Guatemala — along with demand for drugs in the United States to stem both the flow of drugs and people seeking refuge from violence.

"Honduras is the most violent country on the planet," Kelly said, with 91 deaths per 100,000.

He cited as an example of success Plan Colombia, the diplomatic and military initiative started under the Clinton administration to combat leftist insurgents and drug cartels in Colombian territory. He added that he envisions much of the solutions to America’s border and drug crisis in terms of partnerships, investment, information sharing, and tackling America’s drug epidemic from the demand side of the equation.

"Look at Colombia. They made fundamental changes," Kelly said, adding that Colombians now are "exporters of security" to other South American countries.

In addition to border security, Kelly fielded questions on a wide range of controversial issues, including a proposed registry to restrict Muslim immigration, a border wall with Mexico, and a call for mass deportation of illegal immigrants — proposals likely to face fierce opposition from Democrats in Congress.

When asked about vetting immigrants or refugees entering the U.S., you "do the best you can," Kelly said. He also told lawmakers he does not support any registration of people in the United States based on ethnicity or religion.

Asked about the fate of immigrants living in the country illegally, especially young immigrants protected from deportation by President Obama, Kelly said that "the law would guide him" in every decision he will make if confirmed. He added that he did not anticipate young immigrants who have not committed crimes in the United States being a top enforcement priority.

"There's a big spectrum of people who need to be dealt with," Kelly said. "Those categories would be prioritized. I would guess this category might not be the highest priority for removal."

Widely respected by Republicans and Democrats alike, Kelly's nomination is expected to sail through Congress.

Sen. John McCain, R-Ariz., and former Joint Chiefs Chairman retired Army Gen. Martin Dempsey praised Kelly as they introduced him Tuesday, calling him "superbly well qualified" and a "man of great moral authority" who "says what he knows to be the truth no matter the inconvenience."

"I believe in America and the principles upon which our country and way of life are guaranteed. I believe in respect, tolerance and diversity of opinion. I have a profound respect for the law and will always strive to uphold it," Kelly said in his prepared opening remarks. "I have never had a problem speaking truth to power, and I firmly believe that those in power deserve full candor and my honest assessment and recommendations."

The Associated Press contributed to this report.