Washington ? I. Lewis “Scooter” Libby moved a step closer to a prison cell Thursday when a federal judge refused to delay his sentence while he appeals his conviction on perjury and obstruction charges in the CIA leak case.

Lawyers for the former chief of staff to Vice President Dick Cheney said they would file emergency papers in the hope of overturning the ruling by U.S. District Judge Reggie Walton that denied bail for Libby.

Unless the appeals court intervenes, Libby, 56, would likely have to report to prison in six to eight weeks. That would make him the first former White House official in three decades to serve prison time.

The decision by Walton ratchets up pressure on the White House to decide whether to pardon Libby or commute his 30-month sentence. But the White House said the president would not get involved at this point. “Scooter Libby still has the right to appeal, and therefore the president will continue not to intervene in the judicial process,” the White House press office said in a statement.

Some legal scholars suggested President Bush might eventually choose a middle ground, allowing the conviction to stand but curtailing or eliminating the possibility of prison time.

The politically charged case took a bizarre turn Thursday when Walton announced that he had received a number of “angry, harassing, mean-spirited” letters and phone calls “wishing bad things on me and my family” after sentencing Libby last week.

Without disclosing the contents of the letters, he said he was so concerned that he had decided to keep copies for investigators to pursue in the event he becomes the victim of foul play.