Senior Trump administration officials have visited Texas five days before the election to announce they have completed nearly 400 miles of US-Mexico border wall as they try to show progress on perhaps the president’s best-known campaign promise of 2016.

While most of the wall went up in areas that had smaller barriers, the government built hundreds of miles of fencing as high as 30 feet in a short amount of time — most of it this year.

But crews blasted hills and bulldozed sensitive habitats in national wildlife refuges and on native American land to do it, prioritising areas where they could build more quickly.

The Department of Homeland Security waived environmental and other reviews to expedite construction.

And despite President Donald Trump’s repeated promises that Mexico would pay for the wall, the construction has been funded by US taxpayers for at least 15 billion dollars (£11.6 billion), two-thirds coming from military funding.

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Acting Homeland Secretary Chad Wolf claims much progress has been made on the wall (Joel Martinez/The Monitor/AP)

In Texas’ Rio Grande Valley, where Acting Homeland Security Secretary Chad Wolf and other officials spoke on Thursday, authorities have added just seven miles to sections of stop-and-start fencing. That’s despite the region long being the busiest corridor for unauthorised crossings.

DHS officials have held several events announcing immigration operations this month in states considered competitive in the election. Polls show a tight race in Texas, which has not supported a Democrat for president since 1976. Stephen Miller, a top Trump adviser, told reporters on Wednesday that “we have a president campaigning on having successfully built a border wall.”

Mr Wolf and other officials echoed Mr Trump’s campaign attacks on Thursday at an official government event. Mr Wolf criticised House Speaker Nancy Pelosi, judges who have ruled against the wall, and what he labelled “outright lies in the press”.

Mark Morgan, acting commissioner of US Customs and Border Protection (CBP), claimed he was locked out of his Twitter account for posting support for the wall and alleged without evidence that rolling back Mr Trump’s immigration programs would lead to an “invasion” of immigrants.

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Activist protest in front of the border wall after Acting Homeland Secretary Chad Wolf gave a speech on the other side of the controversial barrier (Joel Martinez/The Monitor/AP)

“The wall system we’re looking at right now, it works,” Mr Morgan said.

Laiken Jordahl, a field campaigner for the Center for Biological Diversity Action Fund, has documented the destruction of sensitive areas along the border.

“We’re seeing this administration just blow up anything in their path in order to build an additional mile of wall,” he said. “None of this is about border security. It’s about inflating this mile count in order to make Trump look tough for re-election.”

Border Patrol Deputy Chief Raul Ortiz said this week that the agency was not pushing to build quickly this year in case Mr Trump loses to Democrat Joe Biden, who has pledged to freeze any border wall construction if he wins.

The Trump administration has enacted other measures to stop border-crossers, including new restrictions on asylum eligibility and a public-health declaration citing the coronavirus pandemic that allows agents to quickly expel most migrants.

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Contractors erect a section of border wall last year, replacing smaller fortifications, along the Colorado River in Yuma, Arizona (Matt York/AP)

As of last week, 381 miles of wall had been completed during the Trump administration. More than 270 miles were built using part of the 10 billion dollars (£7.73bn) Mr Trump took from military funding under a national emergency he declared last year after Congress refused to meet his request for wall funding.

Congress has funded some five billion dollars (£3.87bn) for border barriers under Mr Trump, including more than three billion dollars (£2.3bn) in the last two fiscal years for construction in the Rio Grande Valley and around Laredo, Texas.

Of the more than 150 miles funded by Congress in the last two years, just five miles have been built.