US President Joe Biden’s administration is to build a section of border wall in southern Texas in an effort to stop rising levels of immigration.
Around 20 miles (32km) will be built in Starr County along its border with Mexico, where officials report high numbers of crossings.
Building a border wall was a signature policy of President Donald Trump and fiercely opposed by Democrats.
In 2020, Mr Biden promised he would not build another foot of wall if elected.
But the rising number of illegal border crossings has made the issue a vulnerable one for the president.
More than 245,000 crossings have been made this year, government data shows, and September is expected to be a record month.
“There is presently an acute and immediate need to construct physical barriers and roads in the vicinity of the border of the United States in order to prevent unlawful entries,” Secretary of Homeland Security Alejandro Mayorkas said in an announcement.
Dozens of federal laws have been waived in order to approve construction of the wall, including the Clean Air Act and Safe Drinking Water Act.
The move has angered environmentalists, who say the structures will cut through the habitats of endangered plants and animals.
“It’s disheartening to see President Biden stoop to this level, casting aside our nation’s bedrock environmental laws to build ineffective wildlife-killing border walls,” said Laiken Jordahl, a conservation advocate at the Center for Biological Diversity.
According to a proposal by US Customs and Border Protection, the barriers will consist of large bollards embedded in a concrete base, as well as gates, cameras and CCTV equipment.
Homeland Security said it would use funding secured during Donald Trump’s presidency to build the new section.
It is the first time the Biden administration has used its powers to approve the construction of new walls – something that was done often during Mr Trump’s time in office.
Speaking to Fox News on Wednesday, Mr Trump blamed the president for halting construction and causing a crisis at the southern border.
Mr Biden has been facing increasing criticism over his immigration policies in the wake of a recent surge of migrants crossing into the US.
US Border Patrol apprehended 181,059 people along the southern border in August compared with 132,648 in July, according to the latest data.
Mexico’s president, Andrés Manuel López Obrador, said that 10,000 people arrived at the border every day last week alone.