"You know that I've been complaining very strongly about the ballots, and the ballots are a disaster".
The president also continued his criticism against the states where ballots are mailed automatically to registered voters.
"What country are we in?", he said in Wilmington, Del., after a day of campaigning.
Trump on Wednesday had appeared to suggest that if states got "rid of" the unsolicited mailing of ballots there would be no concern about fraud or peaceful transfers of power.
Republican Senator Mitt Romney, a frequent but rare party critic of Trump, went further, saying that any hesitation on the core constitution guarantee was "unthinkable and unacceptable". Asked by Fox News's Chris Wallace in July, Trump said, "I have to see".
Former HUD Secretary Julian Castro (D) weighed in on Twitter as well, writing that "in one day, Trump refused a peaceful transition of power and urged the confirmation of a Supreme Court justice to hand him an election if the results are contested".
Trump made similar comments ahead of the 2016 election.
"I'm not going to just say yes, I'm not going to say no, and I didn't last time, either", he said.
"I still don't, fully, fully, appreciate exactly how tough it is and that fact is, one of the most important things to do is put black men and women in the position where they can accumulate wealth."
'Fundamental to democracy is the peaceful transition of power; without that, there is Belarus, ' the Utah Republican said in reference to the European country experiencing mass protests as its president sought a sixth term and was secretly sworn in despite the opposition candidate claiming they received 60-70 per cent of the votes. "I will keep you in suspense".
Democrats are crying foul, saying that the process should wait until the results of the election are known, allowing the victor to shape the Supreme Court.
The president's comments came hours after he suggested that he would push forward with filling a vacancy on the Supreme Court because it might be called upon to resolve a disputed election. 'I said, what country are we in? "It's better if you go before the election, because I think this, this scam that the Democrats are pulling - it's a scam - the scam will be before the United States Supreme Court".
However, there is no evidence that ballots sent through the postal service have ever led to significant fraud in United States elections.
Dis dey come as more states dey promote di idea of mail-in voting for November election on top fear of coronavirus.