"My administration has presented Congress with a detailed proposal to secure the border and stop the criminal gangs, drug smugglers and human traffickers. It's a tremendous problem...

[A]s part of an overall approach to border security, law enforcement professionals have requested $5.7 billion for a physical barrier. At the request of Democrats, it will be a steel barrier rather than a concrete wall. This barrier is absolutely critical to border security. It’s also what our professionals at the border want and need. This is just common sense.

The border wall would very quickly pay for itself. The cost of illegal drugs exceeds $500 billion a year — vastly more than the $5.7 billion we have requested from Congress. The wall will also be paid for, indirectly, by the great new trade deal we have made with Mexico...

Some have suggested a barrier is immoral. Then why do wealthy politicians build walls, fences, and gates around their homes? They don't build walls because they hate the people on the outside, but because they love the people on the inside."

Source: Donald Trump, "President Donald J. Trump’s Address to the Nation on the Crisis at the Border," whitehouse.gov, Jan. 8, 2019