President Joe Biden said Friday he was not confident the US election in November would be peaceful, citing incendiary comments by Republican contender Donald Trump, who still rejects his 2020 defeat.
Biden's warning came with lawmakers and analysts voicing concern over increasingly bellicose campaign language ahead of the vote.
Trump - who survived an assassination bid in July and another apparent plot in September - alleged widespread fraud after his defeat to Biden, and pro-Trump rioters riled up by his false claims ransacked the US Capitol.
"I'm confident it will be free and fair. I don't know whether it will be peaceful," Biden told reporters as he discussed the election.
"The things that Trump has said and the things that he said last time out when he didn't like the outcome of the election were very dangerous."
Trump was impeached in 2021 for inciting the insurrection after hundreds of his supporters -- exhorted by the defeated Republican to "fight like hell" -- battered police as they smashed windows at the Capitol and broke through doors.
He has been indicted over what prosecutors allege was a "private criminal effort" to subvert the election that culminated in the violence.
Trump - who is due to return to the venue of his first assassination bid in Butler, Pennsylvania on Saturday - has long been assailed over his violent rhetoric.
Biden made his comments during what was the first appearance of his presidency in the White House briefing room, where he touted his administration's achievements as his vice president, Kamala Harris, battles Trump.
Harris and Trump meanwhile were barnstorming the battleground states that are likely to decide who wins the White House.
Trump campaigned Friday in North Carolina, where he reprised his claims of 2020 voter fraud: "We should get elected, but remember this, they cheat like hell," he said.
He also visited neighbouring Georgia, a swing state narrowly claimed by Biden four years ago but won by Trump in 2016 -- and one of the biggest prizes of the 2024 election map.
The Republican inserted himself aggressively into Georgia politics after his 2020 defeat, pushing for state officials to "find" enough votes to overturn Biden's victory.
Trump, 78, was charged by state prosecutors with racketeering, in a case that is on pause and expected to start up again after the election. He denies wrongdoing.
On Friday Trump joined Georgia Republican Governor Brian Kemp after receiving a briefing on the devastation wreaked by Hurricane Helene, the deadliest storm to hit the US mainland since Katrina in 2005.
Trump has repeatedly spread misinformation about the federal response to the disaster, falsely alleging that funding for relief has been misappropriated by Harris and redirected towards migrants.
Harris, who is neck-and-neck with Trump in all seven swing states, rallied Friday in Michigan - a union stronghold that epitomized the US manufacturing decline of the 1980s.
The Democratic contender accused Trump of jeopardizing Michigan auto jobs.
"This is a man who has only ever fought for himself. This is a man who has been a union buster his entire career," she said at a stop in Detroit.
Later, in the city of Flint, she branded Trump "one of the biggest losers of manufacturing jobs in American history."
Flint is a majority Black city where a 2010s scandal over lead-tainted water highlighted government mismanagement and the disproportionate damage to poor and non-white communities.
She reminded rallygoers that the election is just one month away, and early voting has already begun in several states.
"Folks, the election is here. And we need to energize, organize and mobilize," Harris said.
Earlier her campaign announced the country's first Black president, Barack Obama, would stump for her in Pennsylvania and other swing states from next week as she woos undecided voters in the US heartland.