United States President Donald Trump wants a glass wall to be built along the border with Mexico, The Independent reported on Saturday. Building a border wall to fight illegal immigration was one of the central promises of his campaign.

“One of the things with the wall is you need transparency,” Trump told journalists while travelling on Air Force One to a state visit in France.“You have to be able to see through it. So it could be a steel wall with openings, but you have to have openings because you have to see what’s on the other side of the wall.”

Trump even went on to explain why he wanted a glass wall. “And I’ll give you an example,” Trump said. “As horrible as it sounds, when they throw large sacks of drugs over, and if you have people on the other side of the wall, you don’t see them. They hit you on the head with 60 pounds of stuff? It’s over. As crazy as that sounds, you need transparency through that wall. But we have some incredible designs.”

Trump’s statement made news hours later, when journalists realised he was serious and wanted his comments reported.

Trump also said that a 2,000-mile wall was not required and a wall “anywhere from 700 to 900 miles” would be enough, as mountains and rivers provided “natural barriers”.