WASHINGTON — President Bush spared former White House aide I. Lewis "Scooter" Libby from a 2 1/2-year prison term in the CIA leak case Monday, stepping into a criminal case with heavy political overtones on grounds that the sentence was just too harsh.

Bush's move came hours after a federal appeals panel ruled Libby could not delay his prison term in the CIA leak case. That meant Libby was likely to have to report to prison soon and put new pressure on the president, who had been sidestepping calls by Libby's allies to pardon the former chief of staff to Vice President Dick Cheney.

"I respect the jury's verdict," Bush said in a statement. "But I have concluded that the prison sentence given to Mr. Libby is excessive. Therefore, I am commuting the portion of Mr. Libby's sentence that required him to spend thirty months in prison."

Bush left intact a $250,000 fine and two years probation for Libby, and Bush said his action still "leaves in place a harsh punishment for Mr. Libby."

Libby was convicted in March of lying to authorities and obstructing the investigation into the 2003 leak of CIA operative's identity. He was the highest-ranking White House official ordered to prison since the Iran-Contra affair.

Reaction was harsh from Democrats.

"As Independence Day nears, we are reminded that one of the principles our forefathers fought for was equal justice under the law. This commutation completely tramples on that principle," Sen. Charles Schumer, D-N.Y., said through a spokesman.

Libby's supporters celebrated.

"That's fantastic. It's a great relief," said former Ambassador Richard Carlson, who helped raise millions for Libby's defense fund. "Scooter Libby did not deserve to go to prison and I'm glad the president had the courage to do this."

A message seeking comment from Special Prosecutor Patrick Fitzgerald's office was not immediately returned.

Bush said Cheney's former aide was not getting off free.

"The reputation he gained through his years of public service and professional work in the legal community is forever damaged," Bush said. "His wife and young children have also suffered immensely. He will remain on probation. The significant fines imposed by the judge will remain in effect. The consequences of his felony conviction on his former life as a lawyer, public servant and private citizen will be long-lasting."

A spokeswoman for Cheney said simply, "The vice president supports the president's decision."