More than 90 million people have already cast their ballots in early voting, putting the country on course for its highest turnout in a century.
The election comes amid the ongoing coronavirus pandemic. The US has recorded more cases and more deaths than any other country worldwide, reporting more than 99,000 infections on Saturday alone.
Trump travels across five states in final push for votes
The Republican president had a punishing schedule on Sunday, holding rallies in Iowa, Michigan, North Carolina and Georgia, followed later by Florida - all states where polls suggest a tighter race.
Biden campaigns in Pennsylvania
The Democratic challenger and former vice president meanwhile headed to Pennsylvania, place of his birth and another key state in the election. Mr Trump narrowly won there in 2016 but polls suggest Mr Biden is slightly ahead this year.
Mr Biden also addressed reports that Trump will declare victory on Tuesday night if it looks as if he is ahead.
"The president's not going to steal this election," he told reporters. The Democratic candidate also criticized Mr Trump for encouraging his supporters after some forced a Biden campaign bus to stop on a Texas highway, something the FBI has now confirmed it is investigating./BBC