WASHINGTON — President Biden said Thursday that he “can’t stop” construction of new sections of the US-Mexico border wall because Congress wouldn’t rescind spending on it — despite his Homeland Security secretary waiving 26 federal laws to restart former President Donald Trump’s pet project amid record-breaking illegal immigration.

“The money was appropriated for the border wall. I tried to get them to reappropriate, to redirect that money. They didn’t. They wouldn’t,” Biden told reporters in the Oval Office.

“In the meantime, there’s nothing under the law other than they have to use the money for what it was appropriated for. I can’t stop that,” he insisted.

Asked if he thought the border wall was effective, the president replied, “No.”

Biden’s answer contradicted DHS chief Alejandro Mayorkas, who wrote Wednesday in a document justifying the wall expansion that “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.”

“The United States Border Patrol’s (Border Patrol) Rio Grande Valley Sector is an area of ‘high illegal entry,'” explained Mayorkas, who added: “Therefore, I must use my authority … to install additional physical barriers and roads in the Rio Grande Valley Sector.”

White House press secretary Karine Jean-Pierre on Thursday evaded numerous reporter questions about the inconsistency of Mayorkas saying the wall was needed to halt illegal immigration and Biden saying it was not necessary.

Biden said as a candidate in 2020 that “there will not be another foot of wall constructed on my administration” and halted barrier construction shortly after taking office in January 2021.

However, the Biden administration previously authorized some wall construction, including last year to close four gaps in the border wall near Yuma, Ariz., which had seen large flows of migrants.

The administration said Wednesday it was bypassing the measures — including the Clean Air Act, Safe Drinking Water Act, and Endangered Species Act  — to fast-track construction of new sections of border wall along Texas’ border with Mexico, with Mayorkas saying in his memo he had “sole discretion” to do so.

The waivers streamline a process of reviews and potential litigation to speed along the project, which will consist of about 20 miles of additional wall in Starr County along the Rio Grande in South Texas.

The funding for the new construction was approved by Congress in 2019.

Biden restarted Trump’s wall after about 233,000 migrants were detained for illegally entering the US in August — more than had crossed in already elevated waves in August 2021 and August 2022.

An ABC News poll last month found that Biden has just 23% approval from the public on his handling of immigration and the border, making it a major political liability going into his expected rematch against Trump next year.

Fiscal year 2023, which ended Sept. 30, is on track to break all annual records of illegal immigration, with more than 2.2 million apprehensions already recorded.

Statistics for September have yet to be released.

Fiscal 2022 had 2.38 million Southwest border detentions, up dramatically from 1.73 million the year prior, the first of the border surge under Biden, according to Customs and Border Protection data.