Homeland Secretary Secretary John Kelly said Wednesday that the border wall President Trump is trying to build will combine a concrete wall, less expensive fencing, and technology that can help the U.S. better monitor the border.

Kelly was asked by Sen. Claire McCaskill, D-Mo., on Wednesday whether Trump realizes that the border wall will not end up being 2,000 miles of solid concrete, and Kelly agreed that the wall will vary depending on what's needed in each area of the border.

"The president has told me, 'Kelly, go do it,'" Kelly said at a Senate Homeland Security Committee hearing. "We need to protect the southwest border in any way that that makes sense."

"I have a lot of elbow room," he added. "The president knows that I'm looking at every variation... and I have no doubt when I go back to him and say, 'Boss, wall makes sense here... high-tech fencing makes sense over here, technology makes sense over here,' I have no doubt that he'll go tell me to do it."

In a later response to Sen. John McCain, R-Ariz., Kelly agreed that a "wall" can be seen as a combination of physical barriers but also drones and other technology aimed at enforcing the border.

"In my view, the wall is all of that," Kelly said.

He said border agents themselves would provide input that would help DHS decide where to build a concrete wall, and where fencing or drone monitoring might be enough.

Kelly's answers are likely to satisfy Democrats in particular that the U.S. is not about to build a 30-foot concrete wall that stretches across the whole southwestern border. It may also satisfy Republicans worried about the cost of the wall.

However, Kelly also admitted that in some cases, the federal government would have to take ownership of some of the land needed to build the wall, through the process of eminent domain. "There may be places we have to do it," he said of that possibility.

McCaskill used the hearing to urge Kelly to tell Trump about his expanded definition of the border wall.

"It's embarrassing, it's not going to happen," McCaskill said of Trump's claim that the entire wall will be a concrete barrier.

Despite Kelly's flexibility, he also stressed that tougher measures at the border are needed.

"DHS has already begun to take all appropriate steps to plan, design, and construct a physical wall, using the materials and technology that will most effectively achieve operational control of the southern border," he said in his prepared remarks.

Kelly noted that Trump's 2018 budget blueprint called for $2.6 billion in new funding to boost border security.