UPDATED 11.50AM | President Donald Trump cast doubt on the integrity of the US election again on Sunday, saying a vote count that stretched past Election Day would be a "terrible thing" and suggesting his lawyers might get involved.

With two days to go until Tuesday's election and trailing Democratic rival Joe Biden in opinion polls, Trump raced through battleground states in a late hunt for support, while Biden implored attendees at two rallies in the pivotal state of Pennsylvania to get out and vote.