Donald Trump has reportedly told aides he will pardon them for any laws they might break to build a wall along the US-Mexico border as he rushes to get hundreds of miles of fencing erected before the 2020 election.

The president has ordered officials to ignore environmental rules, fast-track construction contracts valued at billions of dollars and “take the land” needed by eminent domain, according to the Washington Post.

Trump also suggested he will pardon them for any laws broken in the process, allegedly telling aides: “Don’t worry, I’ll pardon you.”

“He said people expected him to build a wall, and it had to be done by the election,” a former official told the newspaper, which spoke to current and former officials working on the wall.

An unnamed White House official told the Post that Trump is joking when he talks about pardons.

In a tweet Trump angrily denied the story, saying: “This was made up by the Washington Post only in order to demean and disparage.”

A signature campaign promise, the president has vowed to finish 500 miles of new fencing before the election and chants of “build the wall” are a regular feature of his rallies. But with the polls little more than a year away and approximately 60 miles so far completed, he is running out of time.

Since 2017, US Customs and Border Protection (CBP) says it has built over 60 miles of its “new border wall system” and expects to finish 450 miles by the end of next year.

It comes after the US supreme court cleared the way for Trump to use around $2.5bn in Pentagon funds on the border in July which the administration planned to use to replace parts of the barrier in Arizona, California and New Mexico.

The Guardian has contacted the White House for comment.

Deputy White House press secretary Hogan Gidley told the Post: “Donald Trump promised to secure our border with sane, rational immigration policies to make American communities safer, and that’s happening everywhere the wall is being built.”