President Joe Biden is under fire from both sides of the political spectrum after his administration announced new border wall construction in Texas.

Mr Biden has said he is 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 and said it was "not a serious policy solution".

But on Thursday, his administration signed off on the construction of the new barriers along the border in southern Texas.

The growing number of migrants in US 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 since the fiscal year began last October.

According to US officials and President Biden, funding for the new border barrier - first announced in late June - was agreed during the 2019 fiscal year, under Mr Trump's presidency.

A senior administration official laid the blame for the new construction on Congress, claiming it resisted efforts to cancel the funds in Mr Biden's first budget request issued in May 2021.

Appropriated funds must be made available for their intended purpose unless a rescission is approved by both the Senate and House of Representatives.

"We have repeatedly asked Congress to rescind this money but it has not done so and we are compelled to follow the law," Homeland Security Secretary Alejandro Mayorkas said.

But Mr Biden's comments and the statement from Mr Mayorkas stand in stark contrast to a notice about the project on the US Federal Registry.

In that, Mr Mayorkas said 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 into the United States in the project areas".

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 that 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 US must take examining the root of migration more seriously," she said.

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".

"The Biden administration is doubling down on the failed policies of the past that have proven wasteful and ineffective," ACLU border strategies director Jonathan Blazer said.

US Border Patrol apprehended 181,059 people along the southern border in August compared with 132,648 in July, according to the latest data.

On Thursday, the administration also announced that it would resume deportations of illegal Venezuelan migrants, about 50,000 of whom arrived at the US-Mexico border in September alone.