Trump says 'solar wall' on Mexican border would pay for itself

[WASHINGTON] US President Donald Trump said he's proposed building a "solar wall" on the Mexican border that would pay for itself by generating electricity.

"We're thinking of something that's unique, we're talking about the southern border. Lots of sun, lots of heat," Mr Trump said at a campaign rally in Cedar Rapids, Iowa.

"We're thinking about building the wall as a solar wall, so it creates energy, and pays for itself. And this way Mexico will have to pay much less money, and that's good. Is that good?"

Mr Trump ran for the presidency on an oft-repeated promise to construct a wall across the 3,207 kilometres Mexican border to stop undocumented immigration.

His speech in Iowa was the first time he has publicly described his proposal to build the wall as a solar power plant, though Politico previously reported that he privately floated the idea to Republican members of Congress in a White House meeting on June 6.

"Think about it, the higher it goes, the more valuable it is. Pretty good imagination, right, good?" Mr Trump said in Iowa.

"My idea."

Mr Trump's first full-year budget, released in May, proposes a US$1.6 billion down payment for new and replacement sections of a border wall. The president has estimated that completing the barrier would cost US$8 billion to US$12 billion, though many experts say the actual cost would be far higher.

His proposal has been met with a cool reception in Congress, where lawmakers of both parties have questioned the utility and cost of a physical barrier across the entire length of the border.

BLOOMBERG