Federal authorities are said to be gearing up to seize private land in the Rio Grande Valley in southern Texas to make room for the wall President Donald Trump wants to build on the US-Mexico border.

About $1.6 billion in funding for a section of fencing was already appropriated in the spending bill Trump signed in March.

News about the pending land seizures comes as the Trump administration takes heat for a "zero tolerance" immigration policy that led thousands of children to be separated from their families at the border over the past several weeks.

The federal government is moving to seize private land in a section of southern Texas to make room for President Donald Trump's border wall.

The land seizures would take place in the Rio Grande Valley, The Texas Tribune reported on Thursday. About $1.6 billion in funding for about 65 miles of fencing was already appropriated in a spending bill Trump signed in March, but it allows only for fencing similar to what is already in place at parts of the border.

Rep. Henry Cuellar, the Democrat who represents Texas' border-straddling 28th Congressional District, reportedly attended a briefing in which federal authorities announced the land seizures. "They said they got the money, they got the authority, and they're going to move on trying to acquire the land," Cuellar told The Texas Tribune.

During congressional testimony in April, the US Customs and Border Patrol commissioner, Kevin McAleenan, cited some of the challenges surrounding land seizures in the region. He said those challenges sometimes had little to do with settling with landowners on price.

"Some of the deeds go back to Spanish land grants and are very complex to really figure out who owns the land," McAleenan said.

"So that's a multistage process — we try to do it in a collaborative and open, consultative manner," he said. "We're able to reach an appropriate price with most landowners, and then we do have to go through courts just to clear title in some other cases."

News that some of the land seizures in the Rio Grande Valley would be moving forward suggests the bureaucratic work is progressing more quickly than anticipated. A Customs and Border Patrol representative did not immediately respond to Business Insider's request for comment on the land acquisitions.

The federal government has taken aggressive measures to acquire private land in the past, using a Great Depression-era law originally designed to fast-track public-works projects to quickly generate new jobs, ProPublica and The Texas Tribune reported in December.

Since taking office, Trump has prodded congressional lawmakers for border-wall funding.

Proposals for that money have frequently been attached to other initiatives, like compromises on the Deferred Action for Childhood Arrivals program and, more recently, the Trump administration's "zero tolerance" immigration policy.

The wall has faced resistance from critics including some Republicans. It is also unpopular among a majority of Americans, according to a Gallup poll out this week.