Ahead of unveiling the budget, the Trump administration has proposed kick-starting President Donald Trump’s signature campaign initiative of the construction of a wall on the border of Mexico and the United States with $4.1 billion in spending through 2018, an official said Wednesday.

Mick Mulvaney, director of the Office of Management and Budget (OMB), added that the president’s budget for the fiscal year 2017-18 would find funds for the wall by making cuts in other departments, but confirmed that "it’s coming out of the treasury.”

 “We wrote it using the president’s own words. ... We went through his speeches, we went through articles that have been written about his policies ... and we turned those policies into numbers,” Mulvaney told reporters, according to Politico. Mulvaney said that the figure comprises the president’s request for $1.5 billion in a supplemental spending bill and $2.6 billion in his fiscal year 2018 budget.

Read: Trump's Mexico Border Wall Could Cost $21.6B, Internal Homeland Security Report Estimates

Mulvaney said $1.5 billion would be used by the Department of Homeland Security (DHS) to test different types of border walls in various areas. However, he did not elaborate further.

“The next question is going to be, ‘How many miles of wall does that build, right? We don’t know the answer to that question because we haven’t settled on construction types, we haven’t settled on where we’re going to start,” Mulvaney added. Overall, the Trump administration will ask for $30 billion for defense and border security and the proposed budget according to Mulvaney will also help bump DHS funding by 6 percent.

The $4.1 billion figure, though much smaller than the estimated wall cost of $21.6 billion (according to an internal DHS report reviewed by Reuters), is still one-tenth of the what former President Barack Obama requested for improving tactical infrastructure along U.S. borders in the current fiscal year, according to Politico. 

Meanwhile, Democrats have warned of a government shutdown if Republicans are adamant about passing the legislation in Congress that would in the coming weeks authorize the construction of the border wall.

"If they put those poison pill amendments in and try to shove them down the American people’s throats, of course, they might be responsible for shutting the government down," Senate Minority Leader Chuck Schumer told reporters Tuesday. "To stick it on a must-pass bill, just like defunding Planned Parenthood, would be a huge mistake and they would be responsible for shutting the government down."

Most recently, residents near the Mexican border in the area of Rio Grande received letters from the DHS, which warned them to relinquish their claims on their land in exchange for payment for the land to be acquired for use by the federal government. The binding document, known as the "Declarations of Taking," informed them that if they refuse to sign the document, their land could still be seized by the government under eminent domain law.