Democratic presidential candidate Joe Biden has accused President Donald Trump of using the language of white nationalism and said he would push for a federal buyback programme to encourage Americans to give up their military-style weapons and ammunition if elected.

The former vice president said in an interview with CNN that the voluntary weapons buybacks would be in addition to his push for renewing a lapsed federal ban on new manufacturing and sales of such firearms, a prohibition he helped win in 1994 as a senator from Delaware, only to watch it expire a decade later.

He accused Mr Trump of “using the language of” white nationalists, including the shooting suspect accused of killing 22 at an El Paso, Texas, Walmart over the weekend.

Yet Mr Biden stopped short of some of his rivals for the 2020 Democratic nomination, including El Paso resident Beto O’Rourke and New Jersey Senator Cory Booker, by declining to call Mr Trump himself a white supremacist.

“I’m not sure what this guy believes, if he believes anything” other than political “opportunity”, Mr Biden said, before adding that the distinctions ultimately do not matter.

“Look at the way he talks about Muslims. Look at the way he talks about immigrants. Look at the way he talks about people of colour,” Mr Biden told CNN.

“He talks about them almost in subhuman terms.”

That, Mr Biden said, coaxes white supremacists from the shadows of American society.

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People attend a candlelight vigil for victims of a mass shooting in El Paso (John Locher/AP)

“This is pure and simple white nationalist terrorism,” Biden said, adding that he supports his support for adopting a US federal domestic terrorism law, a move that could give the Justice Department more avenues to investigate and prosecute certain acts.

Mr Trump on Monday called on the nation to condemn white nationalism, but he did not apologise for his incendiary rhetoric on race, from referring to illegal immigration as an “invasion” to his recent Twitter attacks on black members of Congress.

The president mentioned violent video games and mental illness as variables in a consistent wave of mass killings in the Untied States, but he said nothing about new bans on the kinds of weapons used in the killings.

There is no evidence that playing video games leads to violence, and most people with mental illness are not violent.

When Mr Trump’s nod to video games came up in the CNN interview, host Anderson Cooper noted that Biden was rolling his eyes.

“It’s not healthy to have these games teaching kids this dispassionate notion that you can shoot somebody and just sort of blow their brains out,” Mr Biden said.

“But it’s not in and of itself the reason why we have this carnage on our streets.”

Mr Biden is not alone in pushing more restrictive gun laws.

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Democratic presidential candidate Cory Booker (Meg Kinnard/AP)

There is broad agreement among Democrats on a need to ban the new manufacture and sale of certain military-style weapons and high-capacity ammunition clips, while requiring background checks for all gun sales, including those at gun shows that are now exempt.

Buyback programmes have become more frequently mentioned since the latest massacres.

Mr Biden stressed that an “assault weapons ban” would keep the number of weapons in circulation from expanding and that the buyback program would help bring down the current count.

The former vice president said he knew of no “legal way” to compel people who already own such weapons to give them up.

But he also argued against the notion that the Second Amendment affords an absolute right to any weapon.

“You can’t buy a flamethrower,” he said.

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Presidential candidate and El Paso resident Beto O’Rourke prays during the Hope Border Institute prayer vigil on Sunday (Mark Lambie/AP)

Indeed, the Supreme Court has expressly said that government can regulate firearms.

But Mr Biden, the frontrunner in a crowded race to win the Democratic presidential nomination, said he has no plans to push a national gun registry, like what Mr Booker is proposing.

Asked about California Senator Kamala Harris’s proposals to take executive action to impose tighter gun regulations if Congress does not act, Mr Biden repeated the need for legislation because “the next guy” in the White House can “undo” any executive action which is what he said Mr Trump did to many of President Barack Obama’s executive orders.