Biden encouraged potential voters at a campaign stop in the must-win battleground of Pennsylvania, telling them "make sure to vote because the only way we lose this is by the chicanery going on relative to polling places".

Biden referenced what he said were attempts by Trump to discourage voting, including casting doubt on the security of mail-in ballots and the encouragement of potentially intimidating Republican poll observers.

When asked directly, Trump has repeatedly avoided confirming he will accept the result of the election.

Before leaving the state, Biden told reporters his comments were "taken a little out of context" and said "I'm going to accept the outcome of this election, period".

Biden has previously said that his single greatest concern was Trump trying to "steal" the victory. His campaign has recruited hundreds of lawyers and volunteers to prevent election day chaos.

Trump's campaign has accused Biden of lying and stoking fear.

Election experts have been on edge about the process, given chaos and legal challenges during primary elections held amid the outbreak of the novel coronavirus.

Australian Associated Press