Updated

The head of the Office of management and Budget said Monday that sections of the U.S.-Mexican border wall could be see-through, Politico reported.

Mick Mulvaney was interviewed on a radio show and was talking on how much the border project could eventually cost. He mentioned the sheer size of the wall. He said “when you’re talking about a wall that is, you know, several thousand miles long, there’s going to be certain places where a certain type of wall are more appropriate than others.”

The Government Accountability Office estimates it would cost on average $6.5 million a mile for a fence to keep out people who try to enter on foot and $1.8 million a mile for vehicle barriers. There are currently 354 miles of pedestrian fencing and 300 miles of vehicle barriers, much of it built during President George W. Bush's second term.

Republican leaders in Congress have said Trump's wall would cost between $12 billion and $15 billion. Trump has suggested $12 billion.

TRUMP ADMINISTRATION MAKES FIRST TANGIBLE STEP TO BUILDING BORDER WALL

An internal Homeland Security Department report prepared for Kelly estimates the cost of extending the wall along the entire U.S.-Mexico border at about $21 billion, according to a U.S. government official who is involved in border issues. The official spoke on condition of anonymity because the report has not been made public.

The Homeland Security report proposes an initial phase that would extend fences 26 miles and a second wave that would add 151 miles, plus 272 "replacement" miles where fences are already installed, according to the official. Those two phases would cost $5 billion.

The price tag will depend largely on the height, materials and other specifications that have not yet been defined.

“It just depends on the kind of wall that you want to build, and I don’t think we’ve settled, yet, on the actual construction,” Mulvaney said. “You can do steel, you could do concrete, you could do a combination of concrete and steel. You can supplement it with different types of technologies and so forth.”