Donald Trump has controversially urged American states to shun coronavirus lockdowns after mocking expert advice to wear masks.
The US President's rival Joe Biden has called his handling of the pandemic an "insult" to the victims and warning it won't be stopped by "flipping a switch".
Around 800 Americans are dying every day from Covid-19, with 39 states seeing a drastic spike in fatalies.
Democrat Biden boasts a healthy poll lead over the Republican leader with just days to go before the November 3 election.
However, both candidates are currently criss-crossing the country in a bid to secure votes in swing states which could ultimately decide who ends up in the White House.
Speaking from his home of Wilmington, Delaware, the Democrat said he would not campaign "on the false promises of being able to end this pandemic by flipping a switch".
Biden has refused to rule out further lockdowns and promised to "let science drive our decisions", in stark contrast to Trump, who has pushed for months to get economies open.
"Even if I win, it's going to take a lot of hard work to end this pandemic," the former Vice President said from his home in Wilmington, Delaware.
"I do promise this: We will start on day one doing the right things."
He went on to slam Trump's efforts to tear up the Affordable Care Act - or Obamacare - despite the ongoing pandemic.
"We can't afford four more years of a president, who'd rather spend his time desperately trying to strip people of their healthcare than even once bothering to put forward a healthcare plan of his own," said Biden.
Meanwhile, at a packed rally in Goodyear, Arizona, Trump told supporters Biden would enforce further lockdowns, causing economic collapse.
"If you vote for Joe Biden it means no kids in school, no graduations, no weddings, no thanksgivings, no Christmas, and no Fourth of July together.
"Other than that you'll have a wonderful life. Can't see anybody, but that's alright."
He labelled a second term for him as a "super-recovery", while voting in Biden would mean a "depression" - after global stock markets plunged on Wednesday.
While speaking at an earlier rally in the same state's Bullhead City, Trump mocked Democratic mask mandates.
Apparently referring to a tweet by California Governor Gavin Newsom, advising restaurant customers to "keep your mask on in between bites" - Trump said diners would have to "eat through the mask".
"In California, you have a special mask," he said. "You cannot under any circumstances take it off. You have to eat through the mask. It's a very complex mechanism."
More than 75 million Americans have already voted, around 50 million of them by post, in a record-breaking surge.
The total cost of the election is set to hit $14 billion, double the cost of the previous one in 2016 which saw Trump beat Hilary Clinton.
