Special Counsel Jack Smith, who filed the indictment, declined to comment.

Trump had argued that he was entitled to absolute immunity from the charges, but two lower courts rejected that claim.

The majority opinion by the highest court in the land tossed out or questioned key elements in the indictment.

"Under our constitutional structure of separated powers," Justice Roberts wrote, "the nature of Presidential power entitles a former President to absolute immunity from criminal prosecution for actions within his conclusive and preclusive constitutional authority.

“And he is entitled to at least presumptive immunity from prosecution for all his official acts. There is no immunity for unofficial acts."

Justice Roberts wrote that a president's discussions with the Department of Justice are official acts of the presidency, and he or she is therefore “absolutely immune” from prosecution for such interactions.

The indictment alleges Trump pressured the law-enforcement agency to investigate claims - which were found to be unsubstantiated - that widespread voter fraud had affected the election result.

Justice Roberts wrote that a president's discussions with his vice-president are also official conduct, and Trump is therefore "at least presumptively immune” from allegations that he tried to pressure Mike Pence not to certify Mr Biden’s victory in the 2020 election.

The indictment accuses Trump of inciting the US Capitol riot, citing his tweets and remarks he made outside the White House that day.

But the Supreme Court ruled on Monday that Trump's speech and social media activity on 6 January 2021 were all official acts.

In another blow to the case, the justices ruled that Trump's private records - and those of his advisors - "may not be admitted as evidence at trial".

The opinion raised questions, too, about whether allegations that Trump pressured state officials to change their electoral votes in order to overturn his election defeat constituted unofficial acts, but ultimately left it to lower courts to decide.

"The parties and the District Court must ensure that sufficient allegations support the indictment’s charges without such conduct," said the opinion, raising doubts about the potential viability of the case once the official acts are stripped away.

In her dissent, Justice Sotomayor argued that the ruling would protect a president if he or she ordered US special forces to assassinate a political rival, organised a military coup to hold on to power, or took bribes in exchange for conferring a pardon.

Justice Jackson wrote in a separate dissent that the conservative majority’s ruling “breaks new and dangerous ground” and would “let down the guardrails of the law”.

But Justice Roberts wrote that the “tone of chilling doom” from the dissenters was “wholly disproportionate”.

His opinion said that immunity extends to the “outer perimeter” of the president’s official responsibilities, setting a higher bar for prosecution.

“In dividing official from unofficial conduct, courts may not inquire into the president’s motives,” Justice Roberts wrote. “Nor may courts deem an action unofficial merely because it allegedly violates a generally applicable law.”

This ruling is “among the worst-case scenarios” for the special counsel, says Aziz Huq, a constitutional law expert at the University of Chicago.

“I think it will be important to see if [Jack] Smith can narrow the indictment by eliminating those facts that the Court has ranked as 'official',” he told the BBC.

"This is a major victory for Donald Trump," legal expert Mitchell Epner told the BBC.

He said the trial judge will now have to decide which charges can move forward, and Trump will be able again to appeal against her ruling all the way to the Supreme Court.

The Biden re-election campaign said the ruling did not “change the facts" of what happened on the day of the US Capitol riot.

"Donald Trump snapped after he lost the 2020 election and encouraged a mob to overthrow the results of a free and fair election," the campaign said in a statement.