Donald Trump plans to begin the process of constructing a wall on the southern border in March, sources familiar with the president-elect’s transition team told The Daily Caller News Foundation.

The transition team is planning big spending negotiations with Congress at that time, which will include money for the wall — a platform on which Trump built his campaign for the presidency. He plans to make Mexico pay for the wall directly or indirectly by increasing fees on visas and border crossing cards, enforcing trade tariffs and taxing money transfers abroad.

Trump has said the wall, which will be at least 35 to 50 feet high and made of pre-cast concrete, would cost anywhere from $8 billion to $12 billion.

While about 650 miles of fencing already exist on parts of the 2,000 mile border with Mexico, Trump has promised to build a “real” wall that “actually looks good.”

“I would build a great wall, and nobody builds walls better than me, believe me, and I’ll build them very inexpensively,” he said in his speech announcing his candidacy for the presidency. “I will build a great, great wall on our southern border. And I will have Mexico pay for that wall. Mark my words.”