The former top aide to Vice President Dick Cheney, Lewis Libby, makes his first court appearance Thursday following his indictment last week on charges of lying and misleading investigators in the case of the unmasking of covert CIA officer Valerie Plame.

Mr. Libby has vowed to fight his five-count criminal indictment and is expected to enter a plea of not guilty.

Shortly after the indictment was announced on Friday, Mr. Libby resigned as Vice President Dick Cheney's chief of staff.

Some of President Bush's Republican allies in Congress are urging the public to wait for a trial before pronouncing judgment on Mr. Libby.  Republican Senator John Cornyn of Texas spoke on the ABC program This Week.

"Obviously, an indictment is a serious thing.  But we do have such a thing as a presumption of innocence," said Mr. Cornyn.

Mr. Libby was indicted on charges of perjury, making false statements and obstruction of justice.  The charges were announced by special prosecutor Patrick Fitzgerald.  He has led a nearly two-year investigation into who revealed the identity of CIA officer Valerie Plame.

Ms. Plame is married to ambassador Joseph Wilson, who became a critic of the Bush administration's rationale for going to war in Iraq.  Mr. Wilson believes administration officials revealed his wife's identity as a way of retaliating against him, a charge they deny.

Special prosecutor Patrick Fitzgerald did not bring any charges related to the unmasking of Valerie Plame.  Revealing the identity of a covert CIA officer under certain circumstances is a violation of law.

But Mr. Fitzgerald said the alleged attempt by Lewis Libby to mislead investigators about his conversations with journalists concerning Ms. Plame should be taken seriously.

"We need to know the truth and anyone who would go into a grand jury and lie and obstruct and impede the investigation committed a serious crime," said Mr. Fitzgerald.

Opposition Democrats have seized on the Libby indictments to press for a fresh look at whether the Bush administration manipulated intelligence on Iraq's mass weapons program to justify the U.S.-led invasion.

On Tuesday, Senate Democratic leader Harry Reid forced the Senate into a surprise closed session to demand Republicans follow through on a promise to finish a Senate investigation on the handling of the intelligence on Iraq.

"The Libby indictment provides a window into what this is really all about, how this administration manufactured and manipulated intelligence in order to sell the war in Iraq and attempt to destroy those who dared to challenge its actions," said Mr. Reid.

Majority Republicans agreed to a six-member bipartisan task force from the Senate to report on the progress of the intelligence investigation within two weeks.

But the agreement came only after Republican leaders expressed anger at the Democrats' tactics.

Bill Frist is the Senate Republican leader.

"They have no conviction.  They have no principles.  They have no ideas," said Mr. Frist.

In announcing the Libby indictment last week, special prosecutor Fitzgerald said the alleged violations of law came in the course of the investigation, and should not be seen as part of the ongoing debate on the war in Iraq.

"People who believe fervently in the war effort, people who oppose it, people who have mixed feelings about it, should not look to this indictment for any resolution of how they feel or any vindication of how they feel," said Mr. Fitzgerald.

But members of Congress from both parties predict a trial involving Lewis Libby will likely provide an in depth look at how the Bush administration dealt with intelligence on Iraq as part of its effort to convince the American public on the need to oust Iraqi leader Saddam Hussein from power.