President Donald Trump said Thursday that he's not sure November's election will be "honest" because of the use of unsolicited ballots, extending his baseless assertion that widespread mail-in voting is rife with fraud and again casting doubt on if he will accept the results of the election.

"We have to be very careful with the ballots, the ballots, that's a whole big scam," Trump falsely told reporters before departing the White House on Thursday, referring to unsolicited mail-in ballots that only nine states and Washington, DC, provide.

The November contest, he said, needs to be "honest," adding that, "I'm not sure that it can be, I don't know that it can be with this whole situation, unsolicited ballots, they're unsolicited, millions being sent to everybody."

The President's comments come as he continues to lean into a conspiratorial message around the US voting process and build on his pointed refusal Wednesday to commit to providing a peaceful transition of power after Election Day.

"Well, we're going to have to see what happens," Trump said when asked whether he'd commit to a peaceful transition, one of the cornerstones of American democracy.

He has previously refused to say whether he would accept the election results, echoing his sentiments from 2016 that he'll "have to see." And Trump has joked -- he says -- about staying in office well past the constitutionally bound two terms.

But the President's refusal to guarantee a violence-free transition went further and is likely to alarm his opponents, who are already on edge given his deployment of federal law enforcement to quell protests in American cities.

Earlier Thursday, White House press secretary Kayleigh McEnany did not explicitly say the President would accept the results of the election, only saying Trump would "accept the results of a free and fair election."

However, the President himself continues to cast doubt on whether he will view this election as "free and fair."

While rare instances of voter fraud from mail-in ballots do occur, it is nowhere near a widespread problem in the US election system.

Mail ballot fraud is exceedingly rare in part because states have systems and processes in place to prevent forgery, theft and voter fraud.

These systems would apply to both absentee ballots and mail-in ballots for in-state voters.

Additionally, the President's distinction between mail-in voting and absentee voting has baffled experts who say those voting systems are essentially the same thing.

"No-excuse mail voting or absentee voting -- whatever you call it -- is essentially the same thing," David Becker, founder of the nonpartisan Center for Election Innovation and Research, previously told CNN.

"You request a ballot, you get a ballot, you vote, you send it in, and there are protections in place. It doesn't matter whether you call it mail voting or absentee voting. It's the same thing."