President Joe Biden is under fire from both Republicans and Democrats after his administration announced new border wall construction in Texas.
Mr Biden said he was unable to stop the work because the funding was signed off while Donald Trump was president.
Members of his Democratic Party said walls did not work, while rival Republicans accused him of hypocrisy.
Some 20 miles (32km) of barriers will be built in a sparsely populated stretch of the Rio Grande Valley.
While campaigning for president in 2020, Mr Biden promised he would not build another foot of wall if elected. He said it was "not a serious policy solution". But on Wednesday, his administration used its sweeping executive powers to waive more than two dozen federal laws, including some that are designed to protect wildlife, to allow more barriers to be built along the US-Mexico border in southern Texas. In a notice announcing these waivers, Homeland Security Secretary Alejandro Mayorkas said there was an "acute and immediate need" for the construction.
It prompted swift criticism from both major parties as well as from environmental activists and human rights groups.
Mr Mayorkas said the Biden administration was required under law to use the money Congress allocated in 2019 for border barriers.
"I tried to get them to redirect that money. They didn't, they wouldn't," Mr Biden said. "I can't stop that."
He repeated that he did not think border walls were effective.
In a later statement, Mr Mayorkas rejected the claim that the administration had changed its border policy by signing off on the new construction.
"This administration has made clear that a border wall is not the answer," he said. "That remains our position and our position has never wavered."
But the comments did little to stem the criticism from all sides.
On Thursday, the administration also announced that it would resume deportations of illegal Venezuelan migrants, about 50,000 of who arrived at the US-Mexico border in September alone. The growing number of migrants in cities such as New York has become a challenge for the president who has faced intense criticism over his handling of the border.
US authorities have detained more than 2.2 million migrants along the US-Mexico border since last October.
Building a border wall was a signature policy of Donald Trump as president and was fiercely opposed by Democrats, including Mr Biden.
Mr Trump himself said this new construction showed "I was right".
"Will Joe Biden apologise to me and America for taking so long to get moving?" he wrote in a post on his Truth Social platform on Thursday.
Republicans also criticised Mr Biden for what they see as an abrupt pivot to policies he campaigned against.
"He did not think walls work, which is total insanity," North Carolina Republican Representative Ralph Norman told the BBC. "What's changed? I'll tell you what's changed - the American people are sick and tired of seeing their cities overrun."
Democrats, meanwhile, also took aim at the president.
Representative Henry Cuellar, whose district encompasses Starr County where the new construction will take place, told the BBC he does not believe his constituents will be happy with the announcement.
"I am still against a 14th-Century solution - called 'the wall' - for a 21st-Century problem," he said. "I want to see more personnel, more technology".
Democratic Congresswoman Alexandria Ocasio-Cortez called it a "cruel policy" and has urged President Biden to "reverse course".
The Biden administration is also facing criticism from advocacy groups such as the American Civil Liberties Union, or ACLU, which called the decision "a profound failure".