"Yes, we will build a wall," he told a crowd in Cedar Rapids, Iowa. "We have to stop the drugs from flowing in."
"I will give you an idea that nobody has heard about yet," he said. "The southern border. Lots of sun, lots of heat. We are thinking about building a wall as a solar wall. So it creates energy. And pays for itself."
"Think of it, the higher it goes, the more valuable it is," he enthused.
"Pretty good imagination, right? My idea!"
More From This Section
The US administration put out a call for proposals several months ago for the construction of the border wall, one of which -- submitted by a Las Vegas businessman named Tom Gleason -- involved using solar panels.
The Trump administration has yet to make serious headway on the president's emblematic but hugely costly campaign pledge to build a wall on the Mexican border.
The real funding battle will play out starting in October, when 2018 budget negotiations begin in earnest.