Washington DC - Most of Joe Biden's clean energy tax credits are now law and are unlikely to be reversed by Donald Trump if he wins November's presidential election, a senior administration official said Friday.

The 2022 Inflation Reduction Act (IRA) – one of Biden's most significant policy achievements as president – contains tax credits, subsidies, and grants worth hundreds of billions of dollars designed to turbo-charge America's energy transition.

The legislation has been opposed by some Republicans, including Trump, who is reportedly looking at ways to gut Biden's signature law if he wins in November.

But speaking in Washington on Friday, White House national economic advisor Lael Brainard said that even if Trump succeeds in replacing Biden as president, he will struggle to reverse some of the most crucial elements of the IRA.

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"The Inflation Reduction Act clean energy tax credits are the law of the land," she said in an event streamed online. "And under any scenario, I would expect the law to be implemented faithfully."

Brainard said 100,000 Americans had already taken advantage of Biden's electric vehicle tax credit, adding that 21 of the 24 credits were now operative, with the rest due to kick in next year.

"These rules are complex, they take a very long time to write, and they take a very long time to amend," she said.

"And I will say the investor community, the business community, the labor community, they are going to strongly advocate for these projects," she continued.

"And although many of the Republican members opposed the Inflation Reduction Act, they are now loudly cheering on the investments that are in their districts," she added.

Trump has rejected the science behind climate change and, as president, pulled the US out of the Paris climate accord to limit global warming.