WASHINGTON – At his first appearance in federal court, a former top White House aide, I. Lewis Libby, entered a plea of not guilty yesterday to felony obstruction of justice and perjury charges stemming from an investigation into the leak of a CIA operative’s identity.

“With respect, your honor, I plead not guilty,” Mr. Libby told Judge Reggie Walton during the 10-minute arraignment.

Mr. Libby, 55, resigned as Vice President Cheney’s chief of staff last week after the five-count indictment was returned.

Judge Walton allowed Mr. Libby to remain free pending trial, after the special prosecutor handling the case, Patrick Fitzgerald, indicated he would not seek bail. “We do not object to releasing Mr. Libby on his own recognizance,” Mr. Fitzgerald said.

After the hearing, Mr. Libby spent about an hour in the basement of the courthouse, being photographed and fingerprinted by federal marshals.

Mr. Libby, who is on crutches due to a recent foot injury, was mum as he emerged to brave a pack of camera crews and journalists gathered outside the courthouse. He stood by as one of his lawyers, Theodore Wells Jr., vowed that the former White House aide will mount a vigorous defense.

“Mr. Libby has pled not guilty to each and every account in the indictment,” Mr. Wells announced. “He has declared that he intends to fight the charges in the indictment. And he has declared that he wants to clear his good name. And he wants a jury trial.”

Mr. Libby’s defense will be directed by Mr. Wells, who is a partner at Paul Weiss in New York, and William Jeffress Jr., a partner in the Washington office of a Houston-based firm, Baker Botts.

During yesterday’s court session, the new defense team raised the possibility that the trial of Mr. Libby could be delayed by legal wrangling over the duties of journalists to testify or produce notes that may be sought by the defense. “There may well be First Amendment issues in discovery in this case, and in obtaining the evidence necessary for trial,” Mr. Jeffress said. He predicted that such conflicts could lead to “protracted litigation.”

An earlier dispute between the prosecutor, Mr. Fitzgerald, and two journalists involved in the case, Matthew Cooper of Time Magazine and Judith Miller of the New York Times, was litigated all the way to the Supreme Court and resulted in Ms. Miller spending nearly three months behind bars for refusing to testify before a grand jury.

Mr. Libby is accused of lying to FBI agents and the grand jury during the two-year investigation, which was launched after the name of a CIA operative, Valerie Plame, appeared in the press in July 2003.The disclosure came soon after Ms. Plame’s husband, Joseph Wilson IV, published an op-ed piece disputing evidence President Bush cited that Iraq was seeking nuclear materials in Niger.

To accommodate an unusually large crowd of spectators, the proceeding was moved from Judge Walton’s usual courtroom to a larger, ceremonial courtroom elsewhere in the building. The prosecution and defense lawyers sat at folding tables at the front of the room, which can seat up to 200 and was slightly less than full for yesterday’s brief session.

Judge Walton set the next hearing in case for February. Lawyers on both sides said special processes needed to handle classified information related to the matter may cause delays. “I want to try and have the matter heard as expeditiously as possible,” the judge said.

Mr. Fitzgerald said he estimated that the government case against Mr. Libby would take two weeks to present to a jury. He said he hoped to “try the case in a simple fashion” that avoids reference to the classified material. Defense lawyers said they could offer no prediction on timing until they see the evidence in the case.

Mr. Wells is best known in the capital for his defense of a former agriculture secretary under President Clinton, Alphonso Espy, who was acquitted in 1998 of 30 charges relating to gifts from businesses regulated by his department. Mr. Clinton later paid a public tribute to Mr. Wells for his role in winning the acquittal of Mr. Espy.

The defense team gave no hints about its trial strategy yesterday, but last week a lawyer for Mr. Libby signaled in a statement that the former White House aide will argue that any inaccurate statements he may have made were unintentional and the product of a hectic work schedule.

If Mr. Libby’s defense finds itself in a First Amendment showdown with the press, Mr. Jeffress will bring an interesting perspective to the fight. A decade ago he represented ABC News in a the trial of a lawsuit brought by a supermarket chain, Food Lion, over claims that ABC producers broke the law during an undercover investigation of sanitary practices at the grocery stores. A jury awarded $5.5 million to Food Lion, but the award was cut to just $2 on appeal.

A professor at the University of Minnesota who specializes in press law issues, Jane Kirtley, said she was not surprised that Mr. Libby’s case could lead to further clashes between the legal system and the press. “It has often been the case that in a trial where journalists’ testimony is involved that there is a whole sideshow that is created as journalists resist the subpoenas,” she said. Ms. Kirtley said defense lawyers are unlikely to respect agreements Mr. Fitzgerald made to limit the scope of his questioning of reporters caught up in the case.

During the hearing yesterday, Mr. Fitzgerald informed the judge that at an earlier stage Mr. Jeffress represented a witness in the case. Outside of court, Mr. Jeffress declined to name the witness he represented earlier, but a source familiar with the case said it was a former communications adviser to Mr. Cheney, Mary Matalin. She did not return a call seeking comment for this story.

So far, Mr. Fitzgerald has not brought charges against another White House official whose conduct came under close scrutiny in the probe, Karl Rove. In recent days, prosecutors have continued to follow up leads related to Mr. Rove, who is a deputy chief of staff and the top political adviser to Mr. Bush.