Building a wall on the US-Mexico border to stop the influx of refugees and undocumented migrants coming from Central and Latin America was a hallmark of Trump's presidential campaign.

There were about 125.82 million households in the United States in 2016, according to website Satista, which gathered data from the USA census Bureau. The proposed wall could cost each American family around $170. After winning election, Trump changed his position: USA taxpayers would pay up front for the wall, and Mexico would reimburse us (somehow) on the back end. A new fence would cost.

Department of Homeland Security Secretary James Kelly says he wants to break ground on the project in July, with a deadline of completion by 2019.

The report says the border wall would be built in three phases covering just over 1,250 miles (2,000 km) by the end of 2020. This will join the 654 miles of wall previously fortified by President George W. Bush, and will cover almost the entire 2,000 mile border.

Buying private land in order to erect the barrier was one reason for the higher price tag, Reuters said.

It also takes into account the cost of potential legal battles. Last month, Mr. Trump said construction of the wall between the US - Mexico border would begin within months.

A new report from the Department of Homeland Security, unearthed by Reuters, contains a far higher estimate: $21.6 billion.

A White House spokeswoman said it would be "premature" to comment on a report that has not officially been presented to the president.

The report assumes Congress will provide funds by April or May, which aims to allow DHS to find contractors and start construction in September, Reuters stated. The report estimated that agreement alone could bring the cost from $11 million per mile to $15 million per mile in one area.

On Wednesday, the president told a Washington D.C. meeting of law enforcement officials gathered from around the nation that "the wall is getting designed right now".

He also can not retreat on his repeated insistence that Mexico will pay for the construction, a promise that was largely viewed as a fantasy even before the cost of the construction was revealed to be far higher than Trump originally claimed.