Scranton, Pennsylvania - Joe Biden on Tuesday made a campaign trip to his beloved birthplace in Scranton, Pennsylvania, unleashing a blistering condemnation of Donald Trump, who was languishing in court.

The 81-year-old US president even visited his childhood home in the former mining town as he contrasted his blue-collar roots with the election rival he branded a self-obsessed billionaire.

In a speech calling for the wealthy to pay more taxes, Biden said he "learned a lot here in Scranton."

"I learned that money doesn't determine your worth."

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"People like Donald Trump learned very different lessons... he learned that telling people 'you're fired' is something to laugh about," he added, referring to Trump's catchphrase on the reality TV show The Apprentice.

Biden made no reference to Trump's historic hush money trial in New York, which is keeping the Republican off the campaign trail.

But he repeatedly drew broader contrasts with Trump, saying November's vote was a battle between "Scranton values or Mar-a-Lago values."

"Donald Trump looks at the world differently to you and me," a fired-up Biden said. "He wakes up in the morning in Mar-a-Lago thinking about himself, how he can help his billionaire friends gain power and control and force their extreme agenda on the rest of us."

The Scranton visit kicks off a three-day swing through Pennsylvania, a key swing state Biden narrowly carried in the 2020 election against Trump.

During his Tuesday visit, he drove down an expressway named in his honor and visited his wood-paneled childhood house, where large crowds including school children were cheering.

But there were also plenty of demonstrators flying Palestinian flags and Biden's support of Israel's mass killing of people in Gaza.

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The Democrat's campaign earlier released a social media ad featuring Scranton locals, including a cousin, bashing Trump as rich and selfish.

Biden meanwhile mocked Trump for his recent fundraising advantage over his rival, quipping that if stock in Trump's media group "drops any lower, he might do better under my tax plan than his."

On a more serious note, Biden angrily attacked Trump as a threat to democracy, returning to a theme Democrats hope will resonate with voters.

"He says he'll be a dictator on day one, he promises a bloodbath if he loses, this guy denies January 6," he insisted.