President Donald Trump’s senior policy advisor Stephen Miller said Sunday that a wall on the United States’ southern border “will pay for itself many, many, many times over.”

“How much is the wall going to cost? The President says he’s going to bring the cost down. And can you guarantee that Mexico will pay?” George Stephanopoulos asked Miller on ABC’s “This Week.”

“He can bring the cost of the wall down and he will. And there are many, many ways that we can obtain payment for the wall from our friends to the south,” Miller said.

He said that stopping illegal immigration “will save taxpayers hundreds of billions of dollars.”

“This wall will pay for itself many, many, many times over,” Miller said. “And it’s just astonishing to me that the media is so interested in how much it costs to secure our border and has no interest in the cost of refusing to secure our border.”

“How are you going to guarantee that Mexico is going to pay for this wall?” Stephanopoulos asked. “They have said absolutely not, they will not pay for it.”

“There’s all kinds of things we can do. I’m not going to make news today by announcing what our strategy is going to be,” Miller said. “That’s one thing that’s different between this president and past presidents, is we don’t lay out all of our cards for everybody to see.”

Trump policy advisor Stephen Miller claims proposed US-Mexico border wall “will pay for itself many, many, many times over.” #ThisWeek pic.twitter.com/SNir7aU7OU — ABC News Politics (@ABCPolitics) February 12, 2017

An internal report at the Department of Homeland Security estimated the cost of a border wall with Mexico at $21.6 billion, far higher than cost estimates put forward by Trump or congressional leadership, according to a report published Thursday by Reuters.

In February 2016, Trump claimed the wall would cost $10 billion to 12 billion. In late January of this year, Senate Majority Leader Mitch McConnell (R-KY) said that it would cost $12 to 15 billion, and House Speaker Paul Ryan (R-WI) estimated that it would cost up to $15 billion.