More than 500 business groups across the U.S. are calling on Congress and the next administration to keep former President Donald Trump's tax cuts in place, warning that allowing them to expire at the end of next year would amount to "the largest tax increase in American history."

The U.S. Chamber of Commerce led the hundreds of local chambers and other business organizations in signing an open letter to Washington lawmakers and the next administration on Thursday, saying the 2017 tax reforms have been instrumental in driving growth in the economy – and that doing away with them would cause harm.

"While the impact of a massive tax increase on individual Americans is clear, it is critical for policymakers to understand that the expiration of many pro-growth business tax reforms from the 2017 Tax Cuts and Jobs Act (TCJA) also will dramatically increase costs for families and customers, harm main street businesses, reduce take-home pay for workers, and result in the loss of innovation and American jobs," Neil Bradley, executive vice president and chief policy officer at the U.S. Chamber of Commerce, said in a statement.

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"Pro-growth tax policy doesn’t just grow the overall U.S. economy; it raises wages for American workers and improves standards of living," the statement continued. "Maintaining and improving pro-growth tax policy ensures that the U.S. remains globally competitive, retaining and attracting businesses, jobs, investment, and innovation here at home."

The call from the business groups comes as Trump and rival 2024 presidential candidate Vice President Kamala Harris make their pitches to the American people for their respective tax plans ahead of the November election.

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Harris has vowed to reverse the Trump-era cuts and is proposing to raise the rate that major businesses pay from 21% to 28%. At the same time, the Democratic nominee seeks to increase the federal government's small business tax deduction by tenfold, from $5,000 to $50,000.

Trump, meanwhile, is vowing to cut taxes even beyond his signature legislation from 2017 if he returns to the White House.

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"Our plan will massively cut taxes," Trump said last month at a campaign event at a factory in York, Pennsylvania. "I gave you the best tax cut in history."

FOX News' Paul Steinhauser and Alex Schemel contributed to this report.