Lawyers defending Vice President Cheney’s former chief of staff, I. Lewis Libby Jr., at his ongoing obstruction-of-justice trial in Washington are raising fresh doubts about whether the vice president and his one-time top aide will be called as defense witnesses.

The hedging on possible testimony from Messrs. Cheney and Libby came as the defense asked Judge Reggie Walton to reconsider his ruling last month that Mr. Libby must testify if his lawyers plan to argue that memory failures accounted for any false statements he may have made to the those investigating the disclosure of a CIA officer’s identity.

In a brief filed late Monday, defense lawyers acknowledged telling the court earlier that it was “very likely” that Mr. Libby would testify.

The new brief also describes the list of defense witnesses as “potentially including Vice President Cheney.” At a hearing in December, Mr. Libby’s lead trial counsel, Theodore Wells Jr., said flatly, “We’re calling the vice president.” The special prosecutor, Patrick Fitzgerald, expressed concern that defense lawyers may have unfairly won certain pretrial rulings from the court by suggesting that Mr. Libby would testify. During court proceedings on January 25, the prosecutor said he suspected that the defense might never call the White House aide.

Judge Walton initially said such a move would be “suicide” because the defense had promised the jury that Mr. Libby would take the stand. While Judge Walton backtracked somewhat after Mr. Fitzgerald noted that Mr. Wells made no such promise during his opening statement, the judge said bluntly that he would not allow any mention of memory problems if the defendant does not take the stand.

A top Manhattan defense attorney, Edward Hayes, said yesterday that he would not recommend putting Mr. Libby on the stand. “He’s almost certainly an arrogant, upper-middle-class, white male, and part of an administration which has become highly unpopular. Unless he’s personally a very charming and likable man, which I doubt, I wouldn’t put him on,” he said.

However, Mr. Hayes said he disagreed with Judge Walton’s ruling that Mr. Libby had to testify personally to pursue the so-called memory defense. Jurors have already heard from others about Mr. Libby’s national security duties and his busy schedule. That should be enough to allow the defense to argue that he forgot or jumbled contacts with reporters and other officials, Mr. Hayes said. Other legal analysts have said it will be difficult for the defense to persuade jurors that Mr. Libby’s memory failed him unless he takes the stand. It is possible that the defense still plans for Mr. Libby to testify but is simply preserving its right to argue to an appeals court that, by effectively forcing him to take the stand, Judge Walton violated the former vice presidential aide’s constitutional right to remain silent.

In other trial developments, Judge Walton rejected a request yesterday by a New York Times reporter, David Sanger, to avoid testifying in the case. Defense lawyers want to call Mr. Sanger to testify that during an interview about the trip a former ambassador, Joseph Wilson IV, took to Africa to investigate claims of Iraqi nuclear procurement there, Mr. Libby made no mention of Mr. Wilson’s wife, the CIA officer whose identity was exposed. The testimony could undercut the prosecutor’s suggestion that Mr. Libby was obsessed with that fact and was intent on telling journalists about her affiliation.

Mr. Sanger’s lawyers said his testimony was superfluous because one of Mr. Cheney’s communications aides, Catherine Martin, was present during the interview and could affirm that no discussion was had about Mrs. Wilson, who is also known as Valerie Plame.

An attorney for the Times, George Freeman, said no appeal is planned. He noted that the testimony will likely be brief and will come at the request of Mr. Sanger’s source, not the government.

Jurors in the trial yesterday heard several hours of audio-taped testimony Mr. Libby gave to a grand jury. The defendant was heard saying he had no recollection of talking about Ms. Plame with any of the reporters or officials who have claimed to have discussed the matter with him.

In theory, the defense could call no witnesses at all, arguing that the prosecution requires no rebuttal because it has not even come close to presenting evidence that Mr. Libby is guilty beyond a reasonable doubt. However, the defense filing Monday and the defense effort to enforce subpoenas for testimony from other witnesses suggest that Mr. Libby will not employ the high-risk tactic of declining to put on a case.

In related news, an official who oversees federal classification procedures has reportedly asked the Justice Department to instruct Mr. Cheney’s office to stop stonewalling requests for statistics on information classified and declassified by his office.

The director of the Information Security Oversight Office, J. William Leonard, wrote Attorney General Alberto Gonzales last month, seeking a definitive ruling on the vice president’s duty to report classification and declassification actions, according to a Web log focusing on such issues, Secrecy News.

A spokeswoman for Mr. Cheney, Lea Anne McBride, said her office’s view is that it is exempt from the directive requiring annual reports from executive branch entities with classification authority. “This matter has been thoroughly reviewed and it has been determined that it does not apply to OVP, which has both legislative and executive functions,” she said yesterday in response to an inquiry from The New York Sun.

During preparations for Mr. Libby’s trial, it emerged that Mr. Cheney told his aide to give selected journalists details from an Iraqrelated intelligence report that Mr. Cheney said he persuaded President Bush to declassify. The declassification was unusual, and most senior White House officials were kept in the dark about it.