President Joe Biden has stressed the need for divided Americans to come together as he addressed the nation after Donald Trump was shot in an assassination attempt.
Mr Biden said "politics should never be a political battlefield or, God forbid, a killing field" as he spoke in a televised address from the Oval Office.
"We need to lower the temperature in our politics," he added.
Mr Trump, 78, suffered a bullet wound to his ear in the shooting, which happened early on Saturday evening as he was giving a speech to supporters in Butler, Pennsylvania, about 30 miles (50 km) north of Pittsburgh.
"There is no place in America for this kind of violence, for any violence ever. Period. No exceptions," said Mr Biden in his address.
"We can't allow this violence to be normalised. The political rhetoric of this country has gotten very heated. It's time to cool it down."
He said passions would run high on both sides and the stakes of the election were enormous.
"We can do this," Mr Biden implored, saying the nation was founded on a democracy that gave reason and balance a chance to prevail over brute force.
"American democracy - where arguments are made in good faith. American democracy - where the rule of law is respected. Where decency, dignity, fair play aren't just quaint notions, they're living, breathing realities."
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The attempted assassination sparked condemnation by world leaders, including King Charles.
Buckingham Palace said on Monday the King had written privately to Mr Trump, and it is understood the sentiments are in keeping with that of the British prime minister.
Sir Keir Starmer previously condemned the violence, expressed his condolences for the victims and their families, and wished the former president and those injured a quick recovery.
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They save the Oval Office address for serious times - conflict, typically.
On both counts - serious and conflict - a president's prime-time appearance seemed appropriate.
This was a Joe Biden presentation on the gravity of the current situation, eyeballing an American audience on attritional politics.
Phrases like "political battlefield" and "killing field" offered an extreme warning, the choice of language deliberately stark and arresting.
The King's message was delivered on Sunday via the UK Embassy in Washington. The palace said the contents of the correspondence would be kept private.
The royal's message comes as the Republican National Convention opens in Milwaukee on Monday, and Mr Trump's plane was seen touching down for the four-day event earlier on Sunday.
Mr Trump said in a social media post he was going to delay his trip by two days because of the attempted assassination "but have just decided that I cannot allow a 'shooter', or potential assassin, to force change to scheduling, or anything else".
Meanwhile, a spokesperson for the Secret Service has denied diverting resources away from Mr Trump's rally on Saturday, adding: "Protection models don't work that way.
"As far as 'field office teams' these are the candidate nominee operations teams that are added during election years for the heavy travel tempo," he said in a post on X.
The Secret Service has come under fire for not securing the area where the gunman shot from - which was around 150 metres from the former president.