United States’ president Joe Biden on Saturday appealed to blue-collar workers to support his re-election quest and help him compel the richest Americans to pay more taxes.

‘It’s about time the super wealthy start paying their fair share,’ Biden told hundreds of union workers in the industrial state of Pennsylvania.

The campaign rally was sponsored by the AFL-CIO, a union federation that represents 12.5 million American workers and that formally endorsed Biden and Vice President Kamala Harris a day earlier.

Biden launched his 2024 re-election bid on April 25 but had held no major campaign events before Saturday’s rally.

The president made his pitch as a crowded field of Republicans jostle for the party’s nomination, with Donald Trump the runaway frontrunner despite facing federal criminal charges that he mishandled US government secrets, being impeached twice over allegations of misconduct during his White House tenure, and a swirl of other legal troubles.

Biden made a distinctly populist appeal in Philadelphia, touching on a number of issues aimed at halting a migration of working-class voters away from the Democratic Party.

Biden said pro-union sentiments are not widely shared by fellow elected officials in Washington.

‘There are a lot of politicians in this country who can’t say the word ‘union’ and you know I’m not one of them. I’m proud to say the word, I’m proud to be the most pro-union president in American history,’ he said.

He described blue-collar workers as the backbone of the economy.

‘Wall Street didn’t build America. You did,’ Biden said to cheers.

‘If the investment bankers in this country went on a strike tomorrow, no one would much notice,’ he said. But if union members walked off the job, ‘the whole country would come to a grinding halt.’

Biden vowed to protect Social Security and other benefit programs to help average Americans.

‘When the middle class does well, everybody does well,’ he said, adding that reforms are needed to ensure middle class prosperity, including reforming a tax code that is ‘simply not fair.’

‘How could it be fair, when 55 of the largest corporations in America pay zero in federal income tax on $40 billion in profit?’ he asked.

Biden noted that the number of US billionaires has climbed to about 1,000. He said they pay an average of eight percent federal taxes on their earnings.

‘They paid at a lower tax rate than schoolteachers, than firefighters, probably anyone in this room. It’s time they paid a minimum tax. I don’t mind them being billionaires. Just pay your fair share, man.’

Earlier in the day, Biden took an aerial tour of a bridge on an interstate highway in Philadelphia that collapsed last weekend after a tanker truck caught fire.

He vowed the full support of the federal government in rebuilding the bridge.