Donald Trump has warned that there will be a “bloodbath” if he loses the presidential election in November.

Speaking at a rally in Ohio on Saturday, the former president said the election later this year will be the “most important date” in US history, painting his campaign for the White House as a turning point for the country.

It was not clear what Mr Trump meant by “bloodbath”, with the remark coming in the middle of comments about threats to the US auto industry.

“The date – remember this, November 5 – I believe it’s going to be the most important date in the history of our country,” the 77-year-old told rally-goers in Vandalia, Ohio, repeating well-worn criticisms that his rival, President Joe Biden, is the “worst” president.

Criticising what he said were Chinese plans to build cars in Mexico and sell them to Americans, he stated: “We’re going to put a 100 per cent tariff on every single car that comes across the line, and you’re not going to be able to sell those cars if I get elected.”

“Now if I don’t get elected it’s going to be a bloodbath for the whole – that’s going to be the least of it, it’s going to be a bloodbath for the country. That’ll be the least of it. But they’re not going to sell those cars.”

As Mr Trump’s comment gained traction on social media, Mr Biden’s campaign released a statement calling the Republican a “loser” at the ballot box in 2020 who then “doubles down on his threats of political violence”.

“He wants another January 6 but the American people are going to give him another electoral defeat this November because they continue to reject his extremism, his affection for violence, and his thirst for revenge,” the campaign said, referring to the deadly attack on the US Capitol by Trump supporters in 2021.

Later, Mr Biden spoke at a dinner in Washington, where he also warned of “an unprecedented moment in history”.

“Freedom is under assault... The lies about the 2020 election, the plot to overturn it, to embrace the Jan 6 insurrection pose the greatest threat to our democracy since the American Civil War,” he said.

“In 2020, they failed, but... the threat remains.”

The 81-year-old, who has waved off concerns that he is too old for a second term, leavened his rhetoric with humour.

“One candidate’s too old and mentally unfit to be president,” he said of the presidential race. “The other guy’s me.”

Among the issues Mr Trump is campaigning on is sweeping reform of what he calls Biden’s “horror show” immigration policies, despite the ex-president successfully pressuring Republicans to block a bill in Congress that included the toughest border security measures in decades.

On Saturday he invoked the border again as he reached out to minorities who have traditionally voted Democrat.

He said Mr Biden had “repeatedly stabbed African-American voters in the back” by granting work permits to “millions” of immigrants, warning that they and Hispanic Americans “are going to be the ones that suffer the most.”

For decades Ohio had been seen as a bellwether battleground state, though it has trended more strongly Republican since Mr Trump’s White House win in 2016.