WASHINGTON, April 9 — A senior administration official confirmed for the first time on Sunday that President Bush had ordered the declassification of parts of a prewar intelligence report on Iraq in an effort to rebut critics who said the administration had exaggerated the nuclear threat posed by Saddam Hussein.

But the official said that Mr. Bush did not designate Vice President Dick Cheney's chief of staff, I. Lewis Libby Jr., or anyone else, to release the information to reporters.

The statement by the official came after the White House had declined to confirm, for three days, Mr. Libby's grand jury testimony that he had been told by Mr. Cheney that Mr. Bush had authorized the disclosure. The official declined to be named, because of an administration policy of not commenting on issues now in court. Confirmation that Mr. Bush ordered the declassification was published late Saturday by The Associated Press, which quoted "an attorney knowledgeable about the case." Once it appeared, the administration official was willing to confirm its details.

The official responded briefly via e-mail on Sunday to questions from The New York Times.

Before the invasion of Iraq, the information from an October 2002 National Intelligence Estimate was used by both Mr. Bush and Mr. Cheney to bolster their argument that Mr. Hussein posed a threat, and was trying to reconstitute a nuclear program that was dismantled after the 1991 Gulf War.

The disclosure on Sunday appeared intended to bolster the White House argument that Mr. Bush was acting well within his legal authority when he ordered that key conclusions of the classified intelligence estimate should be revealed to make clear that intelligence agencies believed Mr. Hussein was seeking uranium in Africa.

Moreover, the disclosure seemed intended to suggest that Mr. Bush might have played only a peripheral role in the release of the classified material and was uninformed about the specifics — like the effort to dispatch Mr. Libby to discuss the estimate with reporters.

The explanation offered Sunday left open several questions, including when Mr. Bush acted and whether he did so on the advice or at the request of Mr. Cheney. Still unclear is the nature of the communication between Mr. Bush and Mr. Cheney. Also unknown is whether Mr. Bush fully realized what information Mr. Cheney planned to disclose through Mr. Libby or was aware of the precise use that Mr. Cheney intended to make of the material.

It has been known that Mr. Cheney and Mr. Libby were focused on the uranium issue in June 2003, well before Joseph C. Wilson IV, a former ambassador, wrote an Op-Ed article in The New York Times on July 6, 2003, saying that nothing he had seen on a mission to Niger for the C.I.A. confirmed that Mr. Hussein was seeking uranium.

If Mr. Bush acted that early, it would suggest that the administration was growing concerned as evidence emerged that the intelligence was flawed. But the White House account also appears to separate Mr. Bush from the involvement in the selective release of the information to a few reporters, first Bob Woodward of The Washington Post, then Judith Miller of The New York Times. Both say they met Mr. Libby; neither authored articles about the disclosure after their meetings.

A separate effort was occurring simultaneously at the White House to declassify a significant part of the estimate by July 18, 2003. It is unclear why that process was necessary if Mr. Bush had already authorized the release of the information.

The disclosure that Mr. Bush had spoken with Mr. Cheney about the release of material from the intelligence report on Iraq was made in a legal brief filed last Wednesday by Patrick J. Fitzgerald, the special counsel in the C.I.A. leak case.

Mr. Fitzgerald's brief indicates that Mr. Cheney spoke twice with Mr. Libby about the leak of information from the intelligence estimate. Their first conversation took place sometime at the end of June, according to lawyers with clients in the case. The Washington Post reported Saturday that Mr. Libby provided information from the estimate to Mr. Woodward on June, 27, 2003.

Mr. Fitzgerald divulged the White House leak effort as part of his legal maneuvering to restrict Mr. Libby's access to classified documents for use in his trial on perjury and obstruction charges. Mr. Libby has sought the material in an apparent effort to show that he was primarily focused on the intelligence estimate and might have misspoken when he was asked during the inquiry about his conversations with journalists relating to the identity of Mr. Wilson's wife, Valerie Wilson, a C.I.A. officer.

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