Washington DC - President Joe Biden warned on Monday that the Supreme Court's landmark ruling on presidential immunity sets a "dangerous precedent" that Donald Trump would exploit if elected in November.

The conservative-dominated high court ruled earlier that day that Trump – and all presidents – enjoy "absolute immunity" from criminal prosecution for "official acts" taken while in office but can still face criminal penalties for "unofficial acts."

Trump is facing criminal charges over his attempts to overturn his 2020 election loss to Biden, but that trial had been put on hold while the Supreme Court considered his immunity claims.

"For all practical purposes, today's decision almost certainly means there are no limits to what a president can do. This is a fundamentally new principle, and it's a dangerous precedent," Biden said in a speech at the White House.

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The 6-3 ruling on Monday, split along ideological lines, is set to further delay proceedings in Trump's case as lower courts work through myriad questions raised in the Supreme Court decision.

With only four months left until the presidential election, the delays likely mean the case will not reach trial before voters head to the polls.

"The American people must decide if they want to entrust... once again, the presidency to Donald Trump, now knowing he'll be more emboldened to do whatever he pleases, whenever he wants to do it," Biden said.

Trump was quick to revel in what he called a "big win."

Conservative Chief Justice John Roberts, in his majority opinion, said a president is "not above the law" but does have "absolute immunity" from criminal prosecution for official acts taken while in office.

"The president, therefore, may not be prosecuted for exercising his core constitutional powers," Roberts said.

"As for a President's unofficial acts, there is no immunity," the chief justice added, sending the case back to a lower court to determine which of the charges facing Trump involve official or unofficial conduct.

Both a District Court and an appeals court panel had previously rejected Trump's immunity claims in a historic case with far-reaching implications for executive power.

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Trump is charged with conspiracy to defraud the US as well as obstruction of an official proceeding – when a violent mob of his supporters tried to prevent the January 6, 2021, joint session of Congress held to certify Biden's victory.

The 78-year-old former president is also charged with conspiracy to deny Americans the right to vote and to have their votes counted.

The three liberal justices dissented from Monday's ruling, with Justice Sonia Sotomayor saying she was doing so "with fear for our democracy."

"Never in the history of our Republic has a President had reason to believe that he would be immune from criminal prosecution if he used the trappings of his office to violate the criminal law," Sotomayor said. "In every use of official power, the President is now a king above the law."

"Orders the Navy's Seal Team 6 to assassinate a political rival? Immune. Organizes a military coup to hold onto power? Immune. Takes a bribe in exchange for a pardon? Immune. Immune, immune, immune," she said.

Trump, in posts on Truth Social, welcomed the decision, calling it a "big win for our Constitution and democracy."

"Today's Historic Decision by the Supreme Court should end all of Crooked Joe Biden's Witch Hunts against me," he said.

Trump's original trial date in the election subversion case had been March 4.

But the Supreme Court – dominated by conservatives, including three appointed by Trump – agreed to hear his argument for absolute immunity, putting the case on hold while they considered the matter in April.

Steven Schwinn, a law professor at the University of Illinois Chicago, said the ruling means the case "is going to drag on more and more and longer and longer and well beyond the election."

"To the extent that Trump was trying to drag his feet and extend this beyond the election, he has succeeded wildly," Schwinn said.

The opinion also provides a "roadmap" for a US leader to avoid prosecution for a particular action "simply by intertwining it with official government action," he added.

"That's going to seriously hamstring the prosecution of a former president because the president's official actions and unofficial actions are so often intertwined," he said.

In May, Trump became the first former president to be convicted of a felony in his historic hush money trial. He is set to be sentenced on July 11.