President Trump told reporters in remarks released late Thursday that he is “not joking” about a plan to cover the planned wall on the southern border with solar panels — a plan floated by the president as part of a way to pay for the infrastructure project.

Trump was asked about the project Wednesday night by reporters aboard Air Force One on the way to Paris. When asked if he was joking about plans to cover the wall in panels, Trump said: “No, not joking, no.”

“There is a chance that we can do a solar wall. We have major companies looking at that. Look, there’s no better place for solar than the Mexico border — the southern border,” he said. “And there is a very good chance we can do a solar wall, which would actually look good.”

Trump has floated the idea before, an idea that appears to have the support of some congressional lawmakers and, as Trump noted, has been proposed by some businesses. In June, Trump reportedly mentioned the idea to Republican lawmakers as a way to potentially help pay for the wall, and it appeared to be welcomed favorably by some of the fiscal hawks in the Republican caucus.

“I think it’s innovative,” House Majority Leader Kevin McCarthy (R-CA) told the Wall Street Journal. “To authorize it and to appropriate it wouldn’t cost as much.”

“He’s been looking at a lot of options and this is a new option that he’s been looking at that sounds like it’s got real promise,” House Majority Whip Steve Scalise (R-LA) told the Journal.

Las Vegas contractor Thomas Gleason told NBC’s local affiliate in April about his company’s plan to cover the wall in solar panels — and he even submitted a formal proposal to the federal government. Gleason noted that it would have the additional benefit of being almost impossible for illegal immigrants to climb.

“There’s no place to grab. There are no holes. There’s no gap more than three millimeters,” he said.

Democrats, however, shot down any hopes for their cooperation with the proposal. “The president is still pushing this medieval proposal, now with an absurd twist,” Senate Democratic Leader Chuck Schumer said, comparing it to painting a pony with stripes and calling it a zebra.

Other submissions to the government have included turning it into a tourist attraction or using the wall to store nuclear waste, but the Associated Press reported that Gleason’s proposal included the idea that sales of electricity could cover the cost of construction in 20 years or less, and power could also be sold to Mexico.

Trump told reporters Thursday they were considering “some incredible designs,” what he called a “solar wall” was a very real possibility, and that the 2,000 miles of the border didn’t need a wall throughout. He went on to say:

But we are seriously looking at a solar wall. And remember this, it’s a 2,000 mile border, but you don’t need 2,000 miles of wall because you have a lot of natural barriers. You have mountains. You have some rivers that are violent and vicious. You have some areas that are so far away that you don’t really have people crossing. So you don’t need that. But you’ll need anywhere from 700 to 900 miles.

He also told reporters that progress was already being made on the wall, as the administration is fixing parts of the wall already in existance.

“We’re taking wall that was good but it’s in very bad shape, and we’re making it new. We’re fixing it,” he said. “It’s already started.”

Adam Shaw is a Breitbart News politics reporter based in New York. Follow Adam on Twitter:  @AdamShawNY