US President Joe Biden has ordered the construction of additional sections of border wall along a stretch of the US border with Mexico that has seen a large number of migrant crossings, his administration said on Thursday.

The decision marks a 180-degree shift for Biden, who said at the outset of his term in office that "no more American taxpayer dollars be diverted to construct a border wall." The project was a signature policy under the previous administration of former President Donald Trump.

The president defended the move saying he had no choice, legally. Asked whether he thought border walls do anything to stop migration, Biden replied, "No."

Mexican President Andres Manuel Lopez Obrador said the construction of new sections of the wall would be a move in the wrong direction.

"This authorization for the construction of the wall is a step backwards," Lopez Obrador told a press conference ahead of talks with US Secretary of State Antony Blinken and other senior US officials in Mexico City.

Why is Biden extending the border wall?

Homeland Security Secretary Alejandro Mayorkas said the new section of the wall would be built in the Rio Grande Valley Sector of the border — an area he described as witnessing "high illegal entry."

Some 245,000 people have crossed into the United States at that point during this fiscal year, the Homeland Security secretary said.

A notice in the US Federal Register said there was "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," according to Mayorkas.

The agency also said it needed to waive a number of laws, regulations and other legal requirements "to ensure the expeditious construction of barriers and roads in the vicinity of the international land border in Starr County, Texas."

Mayorkas said the extension would be constructed with 2019 funds appropriated under Trump for border barrier building.

Biden later said he "can't stop" the construction since the law dictates the funding must be used and completed in 2023. He said he had tried to move the money but that Congress had stopped.

Biden backtracks on pledge

The decision came after the number of people crossing the border has been increasing after previously falling after the Biden administration brought in new stricter asylum laws in mid-May.

But poverty and insecurity, especially in countries such as Venezuela and Haiti, have kept forcing people to leave their homes.

Trump seized on the announcement, claiming victory over the decision to extend the wall.

Trump, 77, is the current Republican frontrunner for the presidential nomination with Biden, 80, also planning on running again.

Several US cities have complained about the number of people arriving after crossing the border. The mayor of Eagle Pass in Texas declared a state of emergency after several thousand people arrived in recent days.

Mayor of New York, Eric Adams, set off on a trip on Thursday to visit Mexico, Colombia and Ecuador to tell potential migrants that the city cannot accommodate them.

ab/sms (Reuters, AFP, AP)