Planning documents obtained by The Washington Post show the cost of building 509 miles of barriers averages out to more than $36 million per mile. The documents also show that the government would need to obtain — either by eminent-domain claims or purchases — land that lies under nearly 200 miles of proposed barrier.

At a Sept. 11 meeting at the White House led by adviser Jared Kushner, senior officials discussed a plan that would press lawmakers to backfill — or reimburse — $3.6 billion of Pentagon funds that the administration diverted this year to pay for fence construction, the officials said.

The White House also has requested $5 billion for barrier funding in 2020 through the Department of Homeland Security budget, but if that money is not approved, the administration plans to dip into the Pentagon’s construction budget for the second consecutive year to get another $3.6 billion, said the officials familiar with the plan.

The Democratic majority in the House is adamantly opposed to providing additional funding for the project.