President Donald Trump’s “wall” along the U.S.-Mexico border would be a series of fences and walls that would cost as much as $21.6 billion, and take more than three years to construct, based on a U.S. Department of Homeland Security internal report seen by Reuters on Thursday, February 9.

The report’s estimated price-tag is much higher than a $12-billion figure cited by Trump in his campaign and estimates as high as $15 billion from Republican House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell.

The report is expected to be presented to Department of Homeland Security (DHS) Secretary John Kelly in coming days, although the administration will not necessarily take actions it recommends.

The plan lays out what it would take to seal the border in three phases of construction of fences and walls covering just over 1,250 miles (2,000 km) by the end of 2020.

With 654 miles (1,046 km) of the border already fortified, the new construction would extend almost the length of the entire border, Reuters says.

A DHS spokeswoman said the department does "not comment on or confirm the potential existence of pre-decisional, deliberative documents."

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 said the first phase would be the smallest, targeting sections covering 26 miles (42 km) near San Diego, California; El Paso, Texas; and in Texas's Rio Grande Valley.

The report assumes DHS would get funding from Congress by April or May, giving the department sufficient time to secure contractors and begin construction by September. Trump has said Congress should fund the wall upfront, but that Mexico will reimburse U.S. taxpayers. Mexico has said it will not pay.