Washington (CNN) - Ben Carson says he wouldn't use drones to kill undocumented immigrants -- but he'd order strikes on the caves used to transport people across the United States' southern border.
"There are caves that they utilize. Those caves can be eliminated. There are a number of possibilities -- that could be one of them," Carson told CNN's Jim Acosta Sunday on "State of the Union."
He added emphatically: "I'm not talking about killing people. No people with drones."
Carson, a retired neurosurgeon who is now among the top polling candidates for the Republican presidential nomination, also proposed using military strategists and the National Guard to secure the border.
He suggested last week that he would consider using drones along the border -- but said Sunday that he only meant they could be used to watch porous portions of the border, and to shut down "the caves that are utilized to hide people" by smugglers.
"Drones can help with the surveillance. In no way did I suggest that drones be used to kill people," Carson said.
Following a well-received performance at the first GOP debate and his frequent criticism of Planned Parenthood, Carson has recently seen interest in his campaign rise. In Tuesday's CNN/ORC national poll, Carson placed third after Trump and former Florida Gov. Jeb Bush.
Carson, a retired neurosurgeon who rose to political prominence two years ago with his blistering attack against President Barack Obama's policies at the National Prayer Breakfast, has rallied much of the GOP's conservative Christian base with a cry for greater religious freedoms and his fierce opposition to abortion rights.
Carson says he opposes abortion today, despite a history as "a pretty left-wing Democrat" who once disavowed a television ad he appeared in promoting an anti-abortion ballot measure in Maryland.
Carson said he changed his mind on abortion after thinking through how slavery was eliminated.
"I make no bones about the fact that I used to be a Democrat. I used to be a pretty left-wing Democrat, in fact. Over the course of time, you know, my views have changed very dramatically," Carson said Sunday.
"In 1992, I personally was against abortion, but I was not for causing anybody else to do anything. I was pro-choice in that region," he said. "I've changed because I've learned a lot of things, and I began to think about, if abolitionists a long time ago had said, I don't believe in slavery, but anybody else can do it if they want to, where would we be today? So that changed my opinion about a lot of things."
In 1992, Carson appeared in a video that urged voters to reject a controversial Maryland referendum that sought to make it easier for women to get an abortion. The video, sponsored by anti-abortion group Vote Know, made clear in a tagline at the end that it was urging voters to vote down the measure.
"Life is hectic. And it's sometimes easy to let important decisions be made for us. Ballot Question 6 could be like that," Carson says in the clip.
Soon after, Carson appeared in a press conference in which he backed away from taking a stance on the issue. He said he did not realize the ad would take a political position on the referendum.
"My message is not to vote for or against Question Six, but to educate yourself," he said, adding that he asked Vote Know to pull the clip. "It became quite apparent that there were things that could be easily misconstrued."
But the media avail was sponsored by Maryland for Choice -- a pro-abortion rights organization.
Anti-abortion activists said at the time that political pressure may have caused Carson to back away from his support for their cause.
"He may have said that today, but when he agreed to do the spot, he signed off with approval," Ellen Curro of Vote Know said. "I think he has just gotten tremendous pressure from the other side because of the political nature of this argument."
Abortion rights activists, however, praised Carson's decision to denounce his appearance in the anti-abortion ad.
"I see it as a victory for Dr. Carson to be able to thoughtfully and legitimately explain how he feels about the issue," said Stacie Spector, a member of Maryland for Choice.
Carson's message has resonated with Republican voters. In a CNN/ORC poll earlier this month, he tied with former Arkansas Gov. Mike Huckabee as the best GOP candidate to handle abortion, grabbing 17% of the vote. And he was the considered the top GOP candidate who "best represents Republican values."