US President Donald Trump has refused to commit to a peaceful transfer of power if he loses November’s election.
“Well, we’ll have to see what happens,” the president told a news conference at the White House. “You know that.”
Mr Trump also said he believed the election result could end up in the US Supreme Court, as he again cast doubt on postal voting.
More states are encouraging mail-in voting, citing the need to keep Americans safe from coronavirus.
Every losing presidential candidate in modern times has conceded.
If Mr Trump were to refuse to accept the result of the election, it would take the US into uncharted territory and it is not clear how it would play out.
However President Trump’s opponent, Democrat Joe Biden, has previously said that in this scenario he believes the military would be deployed to remove Mr Trump from the White House.
Mr Trump was asked by a reporter on Wednesday evening if he would commit to a peaceful transfer of power “win, lose or draw” to Mr Biden. The president currently trails his challenger in national opinion polls with 41 days to go until the election.
“I’ve been complaining very strongly about the ballots,” Mr Trump, a Republican, said. “And the ballots are a disaster.”
When the journalist countered that “people are rioting”, Mr Trump interjected: “Get rid of the ballots, and you’ll have a very – you’ll have a very peaceful – there won’t be a transfer, frankly, there’ll be a continuation.”
Back in 2016, Mr Trump also refused to commit to accepting the election results in his contest against the Democratic candidate, Hillary Clinton, which she characterised as an attack on democracy.
He was eventually declared the winner, although he lost the popular vote by three million, an outcome he still questioned.
Mitt Romney, a Republican senator who is a rarity in his party because he occasionally criticises the president, tweeted on Wednesday: “Fundamental to democracy is the peaceful transition of power; without that, there is Belarus.
“Any suggestion that a president might not respect this Constitutional guarantee is both unthinkable and unacceptable.”