Democratic frontrunner Joe Biden has dismissed President Donald Trump’s idea of lowering the capital gains tax as a way to stave off an economic downturn.

Biden said on Tuesday that he would not speculate on whether the U.S. is headed toward a recession, but he said lowering the capital gains tax would not stimulate economic growth.

“What we should be doing is we should be focusing on how you re-empower the middle class,” he told reporters in Prole, Iowa. “We should be rewarding work, not just wealth. We should be raising the capital gains tax and cutting taxes for middle class people.”

While Trump insists the U.S. is “very far from a recession,” he and his economic advisers have been casting about for ways to cut taxes to bolster the economy amid signs of slowing growth that have roiled markets.

On Tuesday, Trump said he could cut taxes by indexing capital gains to inflation without congressional approval, an action the White House has been considering for months that would largely benefit the wealthy.

“We’ve been talking about indexing for a long time,” Trump told reporters at the White House on Tuesday. “And many people like indexing and it could be done very simply. It could be done directly by me.”

But Biden did express support for another policy change the White House is considering -- lowering payroll taxes, which he said worked during the Obama administration.

His comments came after Trump said Tuesday that “a lot of people” would like a cut in payroll taxes, which finance the Social Security and Medicare programs. Although the cut has been under discussion, a White House official said Monday a move isn’t currently on the table.

Indexing capital gains to inflation would slash tax bills when selling assets such as stock or real estate by adjusting the original purchase price so no tax is paid on appreciation tied to inflation. However, such a move would do little to spur economic growth, affects few middle-class taxpayers and could prompt legal challenges, experts say.

“I do think the route the president is going down is a big mistake,” Biden said.

The change in capital gains tax calculation would have little chance of passing Congress, which is why Trump is interested in making the change without legislative approval. The House would likely oppose legislation to make the change, as many Democrats have raised objections to the GOP’s 2017 tax cuts, saying they disproportionately helped the wealthy.

Trump’s comments came as the U.S. economy has shown warning signs that could presage a recession, although economists surveyed by Bloomberg News say there’s only a 35% chance of it hitting within the next year.

Biden assailed Trump’s stewardship of the economy, saying the president “inherited a growing economy from the Obama-Biden administration” that he’s now “squandering.” The former vice president said Trump’s “irresponsible tariff war” with China has hurt farmers and stunted growth for the entire economy.

This article was provided by Bloomberg News.