US President Donald Trump on Thursday told voters just outside his opponent Joe Biden’s Pennsylvania birthplace that the Democrat has sold out American workers and would be a “nightmare” if he got into power.

Trump further told the crowd, Biden is “your worst nightmare”.

On Wednesday, former President Barack Obama slammed Trump’s presidency, saying “he never took it seriously”.

Last week, in a brazen attack on the vice president nominee, Trump called Kamala Harris the “most horrible” member of the US Senate and said he was “surprised” Joe Biden had picked her as his running mate.

The president grudgingly acknowledged late in his 2016 presidential campaign that Obama was American-born.

Trump has chosen the White House South Lawn as the location for his acceptance speech — a controversial decision given that presidents are legally required to separate their campaigning from taxpayer-funded governing.

Since then, Trump has faced accusations of racism, and has embraced other conspiracies.

Last week, Joe Biden leveled fierce criticism at Trump, with his campaign saying the president has resorted to “abhorrent” lies about Senator Kamala Harris’s eligibility to be vice president.

The 2020 US presidential election is scheduled for Tuesday, November 3.