July 2 (Bloomberg) -- Lewis ``Scooter'' Libby, Vice President Dick Cheney's former chief of staff, must go to prison while appealing his conviction for obstructing a CIA leak probe, a U.S. appeals court said.

Libby may be behind bars within weeks after a three-judge panel of the U.S. Court of Appeals for the D.C. Circuit today denied his request for release. The decision will increase pressure on President George W. Bush to decide soon whether to pardon Libby, 56, as the former White House official's supporters have urged.

Libby ``has not shown that the appeal raises a substantial question'' under federal law that would merit letting him remain free, the court said.

Libby was sentenced to 2 1/2 years in prison last month following his March 6 conviction of lying to investigators probing the 2003 leak of Central Intelligence Agency official Valerie Plame's identity. U.S. District Judge Reggie Walton refused to let Libby stay out of prison during his appeal -- which might take more than a year to resolve -- saying that evidence of his guilt was ``overwhelming.''

Libby was convicted of obstructing justice, perjury and making false statements. He resigned as Cheney's top aide upon being indicted in 2005.

`No-Win Situation'

While his supporters are calling for a pardon, congressional Democrats including Senate Democratic Leader Harry Reid demanded that Bush promise not to pardon him. Bush's aides, citing Libby's appeal of his conviction, have said the president would stay out of the case for now.

``This is a no-win situation for Bush,'' David Gergen, who advised Presidents Richard Nixon, Ronald Reagan and Bill Clinton, said last week.

A Cable News Network/Opinion Research survey conducted after Libby's conviction found that 69 percent of respondents opposed a pardon while 18 percent favored it. At the same time, a pro-Libby firestorm is being fanned by self-described conservative bloggers and talk-radio hosts, and many conservative leaders are asking the president to step in.

Libby's lawyers didn't immediately respond to requests for comment. Randall Samborn, a spokesman for prosecutor Patrick Fitzgerald, declined to comment on the appeals court's order.

Cheney had no comment on the court's decision today, according to spokeswoman Lea Ann McBride, who referred a reporter to the vice president's June 5 remarks. In that statement, Cheney said that Libby is ``a man of the highest intellect, judgment and personal integrity'' and expressed hope that the ``system will return a final result consistent with what we know of this fine man.''

Three-Judge Panel

The three-judge appeals panel that issued today's order included Judges David Sentelle, nominated by President Ronald Reagan; Karen LeCraft Henderson, nominated by President George H.W. Bush, and David Tatel, nominated by President Bill Clinton.

Libby could take his bid to stay free to the full D.C. circuit or the U.S. Supreme Court, said Carl Tobias, a law professor at the University of Richmond in Virginia.

The defense team has been ``pretty aggressive about pursuing appeals to date,'' Tobias said. ``It doesn't seem like there's any reason to stop at this point, and they may ultimately prevail in terms of having a stay granted.''

Libby was found guilty of lying to Federal Bureau of Investigation agents and a grand jury probing whether the Bush administration deliberately leaked Plame's identity to retaliate against her husband, Joseph Wilson. In a New York Times column on July 6, 2003, he accused the government of twisting intelligence to justify the invasion of Iraq earlier that year.

Novak Column

Her status as a Central Intelligence Agency official was disclosed eight days later in an article by syndicated columnist Robert Novak.

Novak testified during the trial that Plame's identity was provided to him by then-Deputy Secretary of State Richard Armitage and confirmed by White House political adviser Karl Rove.

Fitzgerald, the special prosecutor appointed to the case, argued at trial that Libby lied about his knowledge of the leak to protect his job. It's a federal crime to knowingly reveal the identity of a covert CIA agent, and the White House had announced that anyone who leaked Plame's identity would be fired. No one was charged with a crime or fired for the leak.

Libby's lawyers argued that national security matters kept him too preoccupied to remember details about the leak. He told a grand jury he learned about Plame from Cheney in mid-June 2003, then forgot about it and thought he heard about her for the first time from NBC journalist Tim Russert a month later.

Russert testified that he never discussed Plame with Libby. Other prosecution witnesses also contradicted Libby's grand jury testimony.

The appeals court case is U.S. v. Libby, 07-3068, U.S. Court of Appeals for the District of Columbia Circuit (Washington).

To contact the reporter on this story: Cary O'Reilly at caryoreilly@bloomberg.net.

Last Updated: July 2, 2007 14:02 EDT