US President Donald Trump has said his planned wall on the Mexican border could feature solar panels.

Mr Trump told supporters at a rally on Wednesday evening in Iowa that a solar wall would “create energy and pay for itself”.

He joked it would mean Mexico “will have to pay much less money” to build the structure.

Mr Trump told a rally in Iowa a solar wall would Mr Trump told a rally in Iowa a solar wall would “create energy and pay for itself” (Charlie Neibergall/AP)

Mr Trump claimed as a candidate that Mexico would fully fund his impenetrable border wall but the Mexican government has rejected that possibility.

The US president also suggested the panels would make the wall “beautiful” and then praised himself by saying, “Pretty good imagination, right?”

The wall, which was a signature campaign promise, has not been at the centre of the White House’s agenda and construction work has not begun.