Director of the Office of Management and Budget Mick Mulvaney said on a radio show Monday the border wall with Mexico could cost anywhere from $8 million to $25 million per mile.

Mulvaney appeared on “The Hugh Hewitt Show” and said that, while he can throw out some cost estimates, the actual cost won’t be clear until it comes time for the 2019 budget, The Washington Times reports.

The White House official also said it’s possible the wall, or at least parts of the wall, could be fencing instead of concrete. The entirety of the Mexico-U.S. border stretches for 1,950 miles.

“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 can do a combination of concrete and steel. You can supplement it with different types of technologies and so forth. So it sort of depends on what you want to build.”

Mulvaney hedging on the nature of the wall contradicts President Donald Trump’s firm stance that the wall will be constructed out of concrete.

Some estimates have placed the total cost of the wall at $14 billion.

Reuters reported in early February that an internal Department of Homeland Security document pegged the cost at up to $21.6 billion, which is far more than the $12 billion figure coming out of the Trump camp.

However, regardless of the cost, Trump has made it an essential part of his campaign platform that Mexico pay for the wall’s construction.

Mexican officials have shrugged his claims off so far, with one Mexican politician recently climbing to the top of the border fence separating the two countries to try and demonstrate how a border wall would be “absurd.”

The question of who precisely will pay for the wall did not come up for discussion during the show, but firms interested in constructing the massive project must submit prototype ideas later this week.

Federal authorities will make a decision on the prototypes around the middle of April.

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