WASHINGTON, United States (AFP) — President-elect Donald Trump doubled down Thursday on linking the deadly New Orleans truck-ramming attack to President Joe Biden’s border policies, even though the attacker was identified as a US citizen and military veteran.

The Republican, hours after the attack early Wednesday morning, claimed to have been vindicated in saying on the campaign trail that “criminals coming in are far worse than the criminals we have in the country”.

Law enforcement later identified Shamsud-Din Jabbar, a 42-year-old Texan, as the driver of the pickup truck who ploughed into a crowd of new year’s revellers, killing 15.

Biden described the attack as “despicable,” and said Jabbar had posted videos online hours before “indicating that he was inspired by ISIS”.

Illegal immigration was a key issue for voters in the election, with Trump campaigning on a promise to carry out the largest deportation programme in American history, often citing the unsubstantiated claim that migrants commit more crimes than US citizens.

Early Thursday, Trump posted again on his Truth Social platform, lamenting that weak leadership and the country’s “open borders” had made it a “laughing stock”.

“The DOJ [Department of Justice], FBI [Federal Bureau of Investigation], and Democrat state and local prosecutors have not done their job,” thundered the Republican, whose victory over Kamala Harris in November brought to a halt his prosecution for a variety of alleged election-related felonies.

“They are incompetent and corrupt, having spent all of their waking hours unlawfully attacking their political opponent, ME, rather than focusing on protecting Americans from the outside and inside violent SCUM that has infiltrated all aspects of our Government, and our nation itself,” said Trump.

Jabbar appeared to have been a real estate agent working in Houston — not an illegal immigrant — and had served as an information technology specialist in the military.

Trump, who has blamed the CIA for John F Kennedy’s assassination, said the agency “must get involved, NOW, before it is too late,” without explaining in what capacity.

He did not explicitly mention the attack but he added: “The USA is breaking down – A violent erosion of safety, national security, and democracy is taking place all across our nation. Only strength and powerful leadership will stop it.”

He posted again Thursday morning to warn that, “Radical Islamic terrorism, and other forms of violent crime, will become so bad in America that it will become hard to even imagine or believe.

“That time has come, only worse than ever imagined,” said Trump.