The chairman of the House Judiciary Committee on Monday threatened to serve subpoenas on former Attorney General John Ashcroft and two others associated with the Bush administration's interrogation policies if they don't agree to testify.

If the three - including John C. Yoo, the former assistant deputy attorney general, and David Addington, Vice President Dick Cheney's chief of staff - do not reply by Friday, "I will have no choice but to consider the use of compulsory process," Rep. John Conyers, D-Mich., wrote in letters to them.

That's Washington-speak for issuing congressional subpoenas, tough talk that Conyers has leveled at the White House before. A previous dispute is being hashed out in federal court, with Conyers' committee suing White House Chief of Staff Josh Bolten and former presidential counsel Harriet Miers for refusing to comply with subpoenas on the firings of federal prosecutors. The White House maintains that their testimony is off-limits from congressional oversight under executive privilege.

On torture policy, the administration appears no more willing to comply with Conyers' requests for testimony and information.

Cheney's counsel, Kathryn L. Wheelbarger, said Addington would not testify at a May 6 hearing as Conyers had requested.

"The chief of staff to the vice president is an employee of the vice president, and not the president, and therefore is not in a position to speak on behalf of the president," Wheelbarger wrote April 18. She suggested that Conyers ask others, such as the attorney general or his designee.

Ashcroft and Yoo, the author of several controversial memos on torture policy, also declined Conyers' invitation. Lawyers for both said they had been advised by the Justice Department that they are not authorized to discuss the matters Conyers cited. They also noted that Ashcroft and Yoo were defendants in lawsuits.

Yoo wrote a secret memo for the Pentagon dated March 14, 2003, which the Pentagon released this month under a Freedom of Information Act lawsuit. It outlines the legal justification for military interrogators to use harsh tactics against al-Qaida and Taliban detainees overseas - so long as they did not specifically intend to torture their captives.

Yoo also referenced one of his earlier legal theories, now repudiated by the Justice Department: The U.S. military was not required to observe constitutional protections against unlawful searches and seizures during domestic operations.

He built upon an earlier Justice Department memo he helped draft that narrowly defined torture and lowered the bar for how so-called enemy combatants could be treated.

Conyers also has invited, and threatened to subpoena, former CIA Director George Tenet, former Undersecretary of Defense Douglas Feith and former Assistant Attorney General Daniel Levin. Those officials have neither accepted nor declined Conyers' invitation, a committee spokeswoman said.