US President Donald Trump has called for a glass wall to be built along the border with Mexico.

He said though it was a "crazy" idea, the wall would need to be see-through to stop passers-by being hit with heavy sacks of drugs being thrown over it.

"One of the things with the wall is you need transparency," he told journalists on a flight to Pairs.

"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 wide of the wall.


Image: Mr Trump made the comments on Air Force One - but initially they weren't taken seriously

"And I'll give you an example. 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."

The comments were made on Thursday to reporters, while Mr Trump was travelling on Air Force One to a state visit in France.

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They came to light hours later, only after journalists realised he was serious and wanted them reported.

Andres Rozental, Mexico's former deputy foreign minister and ambassador to the UK, told Sky News the idea was "the most ridiculous thing I have heard in many, many years".

Image: Andres Rozental said the idea was 'absurd'

He added: "It just doesn't make any sense. It's not true."

Mr Rozental estimated there was a "less than 20% chance that this wall - as he calls it - will ever be built".

He cited tough opposition in the US congress and among communities clustered along the country's border with Mexico as Mr Trump's biggest challenges.

The wall was one of Mr Trump's central promises of his 2016 presidential campaign.