Republican presidential front-runner Donald Trump said Tuesday that his long-proposed wall along the U.S.-Mexico border will cost about $8 billion, which the real estate mogul plans to force Mexico to pay.

"The wall is probably $8 billion, which is a tiny fraction of the money that we lose with Mexico," Trump said on MSNBC's "The Place for Politics 2016" on the day of the New Hampshire primary, reported The Washington Times. "We lose a tremendous amount on trade deficits."

Trump's proposal to build a border wall, along with his other hardline immigration policies such as kicking out all 12 million Latino illegals and temporarily banning all Muslims from entering the country, have become a central theme of his presidential campaign. Tuesday was the first time he put a specific number on the cost of the wall, according to CNN.

Trump said the wall will only cover about half of the land separating the U.S. and Mexico, and will include "big, beautiful doors" to allow some immigrants to return to the country.

"So it's $8 billion, and what we're doing is we have 2,000 miles, right? 2,000 miles," he said. "It's long, but it's not 13,000 miles like they have in China. And of the 2,000, we don't need 2,000 - we need a thousand because of natural barriers, etcetera, etcetera, and I'm taking a price per square foot and a price per square mile, and it's a very simple calculation."

Trump argued that the wall is necessary not only to stop illegal immigration and drug trafficking, but to have a country at all.

"If we don't have a border, we don't have a country. Right now, people are walking in and out like it's nothing," he said. "Heroin comes from the southern border. People are walking across the border loaded up with drugs to places like New Hampshire. They're coming over like mad."

He stressed again that he would make Mexico pay for the wall. "We have an astronomical trade deficit with Mexico. We do so many things for Mexico [and] we lose a fortune dealing in trade with Mexico," he said.

Just days earlier, Former Mexican President Felipe Calderon harshly criticized Trump for pledging to make Mexico pay, calling the idea "stupid" and saying that Trump is "completely crazy" and "not [a] very well-informed man."

"Mexican people, we are not going to pay any single cent for such a stupid wall," Calderon told CNBC in an interview last Saturday. "And it's going to be completely useless."