United States President Joe Biden and his Republican challenger Donald Trump have called on Americans to put aside political divisions and come together after Trump narrowly survived an attempted assassination.

In a six-and-a-half-minute address from the Oval Office on Sunday night, Biden said political violence could not be normalised and that all Americans have a responsibility to “cool it down” when it comes to heated political rhetoric.

“We cannot, we must not, go down this road in America. We’ve travelled it before throughout our history,” Biden said. “Violence is never the answer.”

Acknowledging the sharp differences between Democrats and Republicans, Biden said he would continue to articulate his vision for the country ahead of November’s presidential election but that political disagreements must always be settled at the ballot box.

“Disagreement is inevitable in American democracy. It’s part of human nature. But politics must never be a literal battlefield, or, God forbid, a killing field,” he said.

Biden’s primetime address came as the US absorbed the ramifications of the first attempted assassination to wound a current or former president since the shooting of Ronald Reagan in 1981.

Trump was left with a bloodied face after a gunman on Saturday opened fire at a campaign rally in Butler, Pennsylvania, striking the former president in the ear.

Corey Comperatore, a 50-year-old former fire chief, was killed and several others were injured in the attack.

Investigators are still looking into the motives of the suspected shooter, Thomas Matthew Crooks, 20, who was shot dead by authorities shortly after he opened fire on the rally.

The FBI has said it believes that Crooks, who was registered as a Republican but also donated money to a Democratic-aligned political action committee, acted alone and that it has yet to identify any association with a particular ideology.

The attempted assassination has reshaped an acrimonious race that has seen each candidate portray the other as an existential threat, shifting focus away from weeks of commentary about Biden’s age and fitness following a disastrous debate performance last month.

Biden, who has cast Trump as a serious danger to US democracy, temporarily suspended television advertisements and political messaging in the wake of the attack.

Earlier on Sunday, Biden told reporters at the White House that he had a “short but good conversation” with Trump in a phone call after the attack.

“Jill and I are keeping him and his family in our prayers. We also extend our deepest condolences to the family of the victim who was killed. He was a father, he was protecting his family from the bullets that were being fired,” Biden said.

Trump, who has accused Biden of threatening democracy and weaponising the justice system against him, on Sunday arrived in Milwaukee, Wisconsin ahead of the opening of the Republican National Convention, where he will be formally named the party’s nominee later this week.

In an interview with the Washington Examiner on Sunday, Trump said that he would deliver a “whole different speech” at the convention than the “humdinger” he had originally planned.

“This is a chance to bring the whole country, even the whole world, together. The speech will be a lot different, a lot different than it would’ve been two days ago,” he told the newspaper.

Trump said earlier on his Truth Social platform that Americans should stand united and not let “evil to win”. He said he had decided to attend the convention as planned as “I cannot allow a ‘shooter,’ or potential assassin, to force change to scheduling, or anything else”.

Some high-profile Trump allies have gone on the offensive since the attempted assassination, accusing Biden and the Democrats of creating the conditions for violence.

JD Vance, an Ohio Senator who is considered a top contender to be Trump’s running mate, accused the Biden campaign of portraying Trump as an “authoritarian fascist who must be stopped at all costs”.

“That rhetoric led directly to President Trump’s attempted assassination,” Vance said in a post on X on Saturday.

In his address, Biden, who is trailing Trump in most polls, acknowledged that his record and policies would come under criticism at the convention as part of the normal democratic process.

“We debate and disagree, we compare and contrast the character of the candidates, the records, the issues, the agenda, the vision for America. But in America, we resolve our differences at the ballot box,” Biden said, pledging to continue to make the case for democracy and “action at the ballot box”.

“That’s how we do it, at the ballot box, not with bullets. The power to change America should always rest in the hands of the people, not in the hands of a would-be assassin.”