Donald Trump said Joe Biden would give Americans the 'biggest tax cut ever'. Twice.

The US President, who has repeatedly questioned his opponent's health and fitness to govern over occasions where he has apparently misspoken, himself suffered an embarrassing slip of the tongue during a speech in Pennsylvania.

Trump gave three speeches today in the Commonwealth today, with just eight days to go before the November 3 election.

An apparently confused Trump said Biden would deliver "the largest tax cut in history."

He added: "This is the craziest campaign, right? So all my life I watch politicians saying 'we are going to cut your taxes'

"Right? 'We are going to cut your taxes.'

"And he's so shot. He goes 'we will raise your taxes', I said 'what the hell?'."

He then repeated: "He's going to give you the biggest tax cut in the history of our country, including regulations and all the other stuff, which made it so good for us."

The President has repeatedly referred to Biden as "shot", making repeated claims of gaffes, many of which are from selectively edited footage.

Biden made a small-scale appearance in the city of Chester, near Philadelphia, meeting with about a dozen campaign volunteers and speaking with reporters. Biden said he was "not overconfident about anything" and "with the grace of God" he would win Pennsylvania, the state where he was born.

"I think we're going to win Michigan, I think we're going to win Wisconsin. I think we're going to win Minnesota. I think have a fighting chance in Ohio. I think we have a fighting chance in North Carolina. We have a fighting chance in Georgia," Biden added, referring to other election battleground states.

Biden also stepped up his criticism of Trump's handling of a coronavirus pandemic that has killed roughly 225,000 Americans, saying, "The bottom line is, Donald Trump is the worst possible president, the worst possible person to lead us through this pandemic."

More than 60 million Americans already have cast ballots ahead of the November 3 election, a record-breaking pace that could lead to the highest US voter turnout by percentage in more than a century.