US President Donald Trump has taken the highly unusual step of refusing to commit to a peaceful transfer of power if he loses November’s election.

“We’re going to have to see what happens,” Mr Trump told a media conference Thursday (Australian time).

 “You know that I’ve been complaining very strongly about the ballots, and the ballots are a disaster,” he said.

It is virtually unheard of for a sitting president to express less than complete confidence in the US democratic electoral process.

Mr Trump, for several months, has been mounting a campaign against mail-in voting  by tweeting and speaking out critically about the practice.

Many states are encouraging mail-in voting to keep voters safe amid the coronavirus pandemic.

Mr Trump, who uses mail-in voting himself, has tried to distinguish between states that automatically send mail ballots to all registered voters and those, like Florida, that send them only to voters who request a mail ballot.

Mr Trump has claimed widespread mail-in voting would lead to massive electoral fraud. The five states that routinely send mail ballots to all voters have seen no significant fraud.

Mr Trump on Thursday appeared to suggest that if states abandoned the unsolicited mailing of ballots, there would be no concern about fraud or peaceful transfers of power.

“Get rid of the ballots and you’ll have a very peaceful — there won’t be a transfer, frankly. There will be a continuation,” he said.

Mr Trump previously refused to commit to accepting the election outcome when questioned about it in July.

“I have to see. Look … I have to see,” Mr Trump told Fox News. 

“No, I’m not going to just say yes. I’m not going to say no.”

The campaign of Mr Trump’s Democratic challenger, Joe  Biden, responded to the latest comments saying :“The American people will decide this election. And the United States government is perfectly capable of escorting trespassers out of the White House.”

Republican Senator and former presidential nominee Mitt Romney expressed alarm over Mr Trump’s comments.

“Fundamental to democracy is the peaceful transition of power; without that, there is Belarus,” Mr Romney wrote on Twitter.

“Any suggestion that a president might not respect this constitutional guarantee is both unthinkable and unacceptable.”

David Cole, national legal director for the American Civil Liberties Union, released a statement saying: “The peaceful transfer of power is essential to a functioning democracy. This statement from the President of the United States should trouble every American.”

-with agencies