Barack Obama has blasted Donald Trump saying that he failed to take the coronavirus pandemic and the presidency seriously.

The former president made the comments as he campaigned alongside Joe Biden in Michigan on the final weekend of the 2020 campaign.

Mr Obama, the 44th president, and Mr Biden, his vice president vying now to be the 46th president, held drive-in rallies in Flint and Detroit.

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Addressing the crowd, Obama said he initially hoped "for the country's sake" that Mr Trump "might take the job seriously. He never has."

The former president, addressing voters in dozens of cars in a Flint high school car park, seized on Mr Trump's continued focus on the size of his campaign crowds.

"Did no one come to his birthday party when he was a kid? Was he traumatised?" Mr Obama mocked. "The country's going through a pandemic. That's not what you're supposed to be worrying about."

Mr Biden's campaign announced it was sending Mr Obama to Florida and Georgia on Monday.

"Joe Biden is my brother. I love Joe Biden, and he will be a great president," Mr Obama said on Saturday.

On the campaign trail, Obama also shared a video of him sinking a 3-point shot taking to the basketball court. 

Mr Trump, meanwhile, made an aggressive play for pivotal Pennsylvania.

The president railed against a recent Supreme Court ruling that will allow Pennsylvania to count mail ballots received as many as three days after polls close.

He predicted "bedlam" and "many bad things" as the nation waits for a result.

America has had its worst week of the year, in terms of new Covid infections with more than 99,000 Americans reporting new infections on Friday, a record high, according to Johns Hopkins University.

Mr Trump told Pennsylvania voters that his administration has done "an incredible job" dealing with the pandemic. He promised that the mass distribution of a vaccine was "just weeks away".

With the campaign down to the final days, Mr Trump's closing sprint includes, in addition to the four stops in Pennsylvania, nearly a dozen events in the final 48 hours across states he carried in 2016.

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Mr Biden will close out his campaign on Monday in Pennsylvania, the state where he was born and the one he has visited more than any other.

The Biden team announced that the candidate, his wife, Jill, running mate Kamala Harris, and her husband, Doug Emhoff, plan to "fan out across all four corners of the state".

As of Saturday morning, nearly 90 million voters had already cast ballots nationwide, according to a tally by The Associated Press.

Tens of millions more will vote by the time polls close on Tuesday night.