President Joe Biden warned Monday that the US 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 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."

"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.

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.

The 6-3 ruling on Monday, split along ideological lines, is set to further delay proceedings in that case, almost certainly to sometime after voters head to the polls in November.

"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.

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.

Trump is charged with conspiracy to defraud the United States 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 public has a right to know the answer about what happened on January 6, before they're asked to vote again this year," Biden said.

"Now because of today's decision, that is highly, highly unlikely. It's a terrible disservice to the people of this nation."

'Organize a coup? Immune'

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."

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.

- Election case will 'drag on' -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.

Facing four criminal cases, Trump has been doing everything in his power to delay the trials until after the election.

Trump was convicted in New York in May of falsifying business records to cover up a sex scandal in the final stages of the 2016 campaign, making him the first former US president ever convicted of a crime.

His sentencing will take place on July 11, though his lawyers have sent a letter to the judge in that case seeking to set aside the verdict in light of the immunity ruling, US media reported.

By filing a blizzard of pre-trial motions, Trump's lawyers have managed to put on hold the three other trials, which deal with his attempts to overturn the 2020 election and hoarding top-secret documents at his home in Florida.

If reelected, Trump could, once sworn in as president in January 2025, order the federal cases against him closed.