WATERLOO, United States - Former US president Donald Trump, who has come under sharp criticism for attacks on immigrants which some say hark back to Nazi philosophy, says he's never read Adolf Hitler's manifesto "Mein Kampf."

But he did not hesitate into doubling down on his inflammatory language.

"It's true that they're destroying the blood of our country. That's what they're doing -- they're destroying our country," Trump -- the clear frontrunner for the Republican presidential nomination in 2024 -- said late Tuesday at a rally in Iowa.

The 77-year-old Trump made similar comments over the weekend, sparking a firestorm of criticism, with a White House spokesman accusing him of "echoing the grotesque rhetoric of fascists and violent white supremacists."

Last month, President Joe Biden, who defeated Trump in the 2020 election and could face off with him again in 2024, accused the Republican of echoing Hitler when he described political opponents as "vermin."

On Tuesday night, Trump denied any parallels.

"I never read 'Mein Kampf'," he said, adding that the Nazi leader used such language "in a much different way."

A Biden campaign account on X, formerly known as Twitter, on Wednesday published a graphic juxtaposing three comments from Trump and statements from Hitler.

"This is not a coincidence," the Biden camp said.

Trump's rhetoric has put Republican Party heavyweights in a highly uncomfortable position. Top Republican Senator Mitch McConnell has publicly denounced Trump's remarks.

During his first White House campaign, Trump n 2015 said some immigrants from Mexico were "bringing crime" and "rapists."

He then made his infamous pledge to build a huge wall along the US-Mexico border to keep migrants out. Though hundreds of miles (kilometers) of wall were built, migrant crossings have continued to surge.

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© Agence France-Presse