Report: DHS estimates the cost, time needed to build Trump's border wall

President Donald Trump's border wall, which will actually be made up of a series of fences and walls, is reportedly expected to cost as much as $21.6 billion and take three and a- half years to construct.

That cost estimate came from an analysis by the Department of Homeland Security, according to Reuters, and surpasses the price tag of $12 to $15 billion previously estimated by Senate Majority Leader Mitch McConnell (R-Ky.).

Construction would take place in three phases, according to the report. Currently, 654 miles of the border is already fenced or walled off, so the new construction would barricade the remainder of the perimeter between the U.S. and Mexico.

The first phase would be the smallest, with sections covering land near San Diego, California; El Paso, Texas; and Texas' Rio Grande Valley — a length of 26 miles. The second phase of construction proposed in the report would stretch 151 miles, also near the Rio Grande Valley; Laredo, Texas; Tucson, Arizona; El Paso, Texas; and Big Bend, Texas.

The final phase would cover an unspecified 1,080 miles, effectively sealing off the remainder of the U.S.'s southern border.

The report is expected to be presented to DHS Secretary John Kelly in the coming days.

When Reuters asked about the report, a DHS spokesperson told the outlet that the agency does "not comment on or confirm the potential existence of pre-decisional, deliberative documents."

A White House spokesperson said it would be "premature" to comment on a report that has not yet been formally presented to the president. However, during a meeting with law enforcement on Wednesday, Trump said, "the wall is getting designed right now."

The DHS report accounts for the cost of acquiring private land, which is part of the reason the price tag is so much higher than previous estimates. And Bernstein Research, an investment research group that tracks material costs, determined the cost could be driven up to $25 billion due to uncertainties surrounding the endeavor.

It is important to note, too, that the DHS report does not account for legal battles over eminent domain or major physical barriers — like mountains — that make building in some areas unfeasible. The DHS report does not address specifics about this problem. But on the campaign trail, Trump said during a Fox News interview that there is no need for a wall in some places because the U.S. is protected by mountains and "large and rather vicious rivers."

Trump has long vowed Mexico will foot the bill for the wall. However, since taking office, he has suggested American taxpayers will have to swallow the cost up front but Mexico will ultimately reimburse the U.S.

Mexican President Enrique Peña Nieto said last month that his country "does not believe in walls." He added, "I’ve said time and again; Mexico won’t pay for any wall."

And last week, Sen. John McCain (R-Ariz.), a frequent opponent to the president, cast doubt on Trump's promise that Mexico will pay for the wall, calling it "not a viable option."

The senator also criticized the idea of a wall, telling CNN's Manu Raju that securing the border will take much more than a barrier: "If you only build a wall … without using technology, individuals, drones, observations, etc., you’re not going to secure the border."