A Democratic senator called on the White House Tuesday to require staffers to cancel reporter confidentiality agreements so the journalists might tell investigators whether a Bush administration official leaked a CIA operative's name.

White House press secretary Scott McClellan responded to the request, saying, "It would be unfortunate if people are seeking to politicize a serious matter like leaking classified information for partisan gain."

In a letter sent to White House chief of staff Andrew Card, Sen. Charles Schumer (search), D-N.Y., argued that the White House staff has only "partially cooperated" with Justice Department investigators by turning over phone and e-mail records.

Signing confidentiality waiver forms could persuade reporters to disclose their confidential sources, possibly helping investigators find out if an administration official leaked the name of Valerie Plame (search), an undercover CIA officer, to syndicated columnist Robert Novak in July.

Plame is married to former Ambassador Joseph C. Wilson (search), who has said he thinks his wife's identity was disclosed to discredit his assertions that the administration exaggerated Iraq's nuclear capabilities to build a case for war.

"Professional prosecutors handling the investigation into this national security breach have determined that they would be aided by these waivers of confidentiality," Schumer said. "Full cooperation requires that these staffers comply with this reasonable request from law enforcement."

McClellan declined to say whether the White House, or he personally, had been asked to release reporters from confidentiality agreements. "If there are specific requests being made of individuals, we would not necessarily know what those requests are," McClellan said.

As he has done for days, McClellan referred specific questions to the Justice Department.

"The White House has done everything it has been asked to do," McClellan said. "The president made it very clear that he wants the White House to cooperate fully in this investigation. If anyone has information relating to the investigation, they should provide that information to the officials in charge."

Schumer said "full cooperation" requires freeing journalists from their obligations to protect their sources. "I hope you will do so as soon as possible," Schumer said in his letter to Card.

Schumer said that in the late 1990s when Republican congressional leaders were looking into whether White House officials were leaking information about members of Congress, then White House chief of staff Erskine Bowles informed news organizations that the White House was waiving all confidentiality rights regarding such leaks.

The senator said that while this would be a positive move, he thinks it would be better if White House staffers signed individual waivers. "The only way that will happen is if you order it of your employees," Schumer said. "I encourage you to do so in the strongest possible way."

The FBI has interviewed more than three dozen Bush administration officials. A leaker could be charged with a felony.

Attorney General John Ashcroft removed himself last week from the inquiry to avoid the appearance of a conflict of interest. Democrats, including Schumer, had called on Ashcroft to step aside from the investigation. U.S. Attorney Patrick J. Fitzgerald of Chicago, a career prosecutor, is leading the probe.